Guessing on the GRE: the grand synthesis
After considering all the activity on this one, I think I'll have to nudge my position a bit closer to the opposition. Concerning my objection to Marc Turner's post on being a "good guesser" on the grounds that there's no such thing, I see now that his problem for me wasn't faulty logic but ambiguous phrasing. By "good guesser" he didn't mean someone who could beat the odds but someone who, by chance alone, happened to do better than what would be expected on average. I suggest "lucky guesser" is a less confusing term for what he had in mind. And, contrary to Karl Wuensch's recent post on the topic, "guessing" to me _is_ blind guessing, making a decision when one has absolutely no information on which to base a choice. I compliment Marc for his empirical approach to the issue. But this is one case where collecting data isn't the way to go; logic is. Here's my grand synthesis. Remember, the aim of this exercise is to provide test-taking advice for students: if you absolutely don't know, should you guess or should you leave the question out? Suppose you are clueless. And suppose you are a student (but I repeat myself). If you have absolutely no information on which to base a choice, on average it makes no difference whether you guess or skip the question. But, as Marc points out, that's only in the long run, and sometimes your guessing will bring you more joy, and sometimes less, purely by chance. So in individual cases, a guessing strategy will sometimes help, sometimes hurt. So the advice to a student would be: If you have no basis whatsoever for deciding among the five alternatives, guess if you're a gamblin' man (or woman), or don't guess if you're a cautious sort. But only the very poorest of students answering the very best of questions will find him or herself in this unhappy state of absolute cluelessness. More likely, the student will be able to detect that at least one of the choices is less than what it pretends to be. Then, if you have even the slightest reason to reject even one answer, Lady (or Lord) Luck will turn, ever so slightly, in your favour, and you should certainly take a chance and guess at the remaining choices. I believe this brings me within shouting distance of Nancy Melucci's position (hi, Nancy!), even if we don't exactly correspond. I hope but have my doubts that this will dispose of the issue. -Stephen Stephen Black, Ph.D. tel: (819) 822-9600 ext 2470 Department of Psychology fax: (819) 822-9661 Bishop's Universitye-mail: [EMAIL PROTECTED] Lennoxville, QC J1M 1Z7 Canada Department web page at http://www.ubishops.ca/ccc/div/soc/psy Check out TIPS listserv for teachers of psychology at: http://www.frostburg.edu/dept/psyc/southerly/tips/
Re: What is guessing?
Listmembers - Karl W wrote: "And if this is what Nancy's students understand "guessing" to mean, her telling them not to guess on the SAT is very poor advice indeed!" I have noted and am offended by your patronizing tone. I have been doing this work for four years and I am very explicit about what kind of guessing I mean. We (the tutors) tell them not to WILD guess - not to guess when they have no clue and have not eliminated any of the answer choices. We coach them on all kinds of elimination strategies, in order to help them raise their chances of picking correctly. We also (Dr. Timmerman) help them review and learn all kinds of relevant content in order to become more knowledgeable people as well as better test takers. Standardized test taking is a skill that can be learned, and that appears to control the destiny of many students (or understandably appears to do so.) Many students, both worthy and perhaps not so have figured out that taking a test that has a limited predictive value in determining their success in college, will be a major hurdle. I don't see the moral issue in teaching them to do better on the test, using every legitimate strategy available. Nancy Melucci
balancing frequency of correct answer options
Those of you who try to "balance" the number of times 'a' 'b' 'c' and 'd' are the correct answer options are just giving students another way to "guess" the correct answer without knowing the material. You should use a random process to determine in which position the correct answer will appear. Do that and you might be surprised how often you get "runs" of three or four correct answers in the same position -- we greatly underestimate the probability of such runs in a truly random process. Marc has been telling us that with truly random guessing it may be true that on average the score will not be affected, but some will be lower (and some higher). But that is also true when the "guessing" is not random, even when it follows having with certainty eliminated one of the alternatives. If nothing else, this current discussion has illustrated well that humans, including Ph.D. holding psychologists, do not understand probability very well. ++ Karl L. Wuensch, Department of Psychology, East Carolina University, Greenville NC 27858-4353 Voice: 252-328-4102 Fax: 252-328-6283 [EMAIL PROTECTED] http://core.ecu.edu/psyc/wuenschk/klw.htm
What is guessing?
My dictionary says "to judge or form an opinion from things that make something probable but fall short of sufficient evidence." I think this matches what most people mean by "guessing" -- it is not a blind guess, they have a hunch about it, but are not certain about it. And if this is what Nancy's students understand "guessing" to mean, her telling them not to guess on the SAT is very poor advice indeed! As Kalat and other have demonstrated, "guessing" is not usually blind. For example, there are a number of strategies that examinees can use to get better than chance performance even when they have no knowlege of the tested material -- for example, always choosing the longest answer option (Kalat showed that this strategy works well with the poorly constructed items in typical intro psych test banks -- I always take care to avoid writing MC questions where this strategy would pay off) ++ Karl L. Wuensch, Department of Psychology, East Carolina University, Greenville NC 27858-4353 Voice: 252-328-4102 Fax: 252-328-6283 [EMAIL PROTECTED] http://core.ecu.edu/psyc/wuenschk/klw.htm
Re: Responsibility for missed lectures
I suspect that some students do find it easier to miss class when they know that my extensive notes are available on the web -- but that does not bother me. If the students can learn the material from my notes without attending class, then I am satisfied. But the serious students attend whenever they can, because they know that in class they get the benefit of hearing the interesting exchanges among class members (including me) and they also get to hear my jokes that are too off-color to post on the web ;-) Apparently most of my students actually enjoy attending my classes -- so much so that their (and my peers') evaluation of my teaching has led to my being given this year the highest teaching award in the University of North Carolina system. My head has grown two hat sizes since that event. My wallet grew too (a very nice stipend was included), but that did not last long. ++ Karl L. Wuensch, Department of Psychology, East Carolina University, Greenville NC 27858-4353 Voice: 252-328-4102 Fax: 252-328-6283 [EMAIL PROTECTED] http://core.ecu.edu/psyc/wuenschk/klw.htm - Original Message - > Karl wrote: > All of my lecture notes are in Word files, so I simply convert them to > web > pages and post them where the students can get them if they miss class > or if > they were in class but would like to review my notes. > > Karl, > I used to do this also, but then became concerned that students were > just using these in lieu of attending class. (My notes are pretty > complete.) Did you find this happened? How did you handle it? > Marcia > > Marcia J. McKinley-Pace, J.D., Ph.D. > Assistant Professor of Psychology > Mount St. Mary's College > Emmitsburg, MD 21727 > (301) 447-4282 > [EMAIL PROTECTED] >
Re: Night vision (Student question)
Lots of possibilities -- distribution/density of rods, level of and rate of regeneration of rhodopsin (possibly related to diet -- eat carrots), clarity of any tissue through which light must pass on way to retina. Or, maybe the brother and husband are just better guessers on the SAT. ;-) What most people describe as guessing yields better performance than would be expected by truely random guessing, and this applies to perceptual phenomena too (signal detection theory and all that). - Original Message - From: [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Monday, November 06, 2000 6:15 AM Subject: Night vision (Student question) Folks, Are there any explanations for variations in the acuity of night vision from person to person (other than owning night vision goggles)?
Re: Faces: This message is not about guessing on the GRE
They also have a full-color hard copy catalog which you can order by calling 1 800 962 1141. I am a retailer, in addition to my other positions, and have found that is it usually far easier to call and get catalog than deal with web sites problems and ordering from the web. I have discovered many great wholesale suppliers through the web, but then order their catalogs. Molly Straight, MA Adjunct Lecturer of Psychology Alderson-Broaddus College Philippi, WV - Original Message - From: "Stephen Black" <[EMAIL PROTECTED]> To: "TIPS" <[EMAIL PROTECTED]> Sent: Sunday, November 05, 2000 9:14 PM Subject: Faces: This message is not about guessing on the GRE > Not too long ago, I plaintively complained about my inability to > find an inexpensive source of faces expressing emotions. Marcia > McKinley-Pace came to my rescue with a suggestion about getting a > poster from a teacher supply store. > > She's now provided me with specific information, which I'm happy > to pass on to the rest of you. The emotion posters can be > purchased from: > > ChildsWork/ChildsPlay at http://www.childswork.com/ > > where they can be viewed and ordered on-line, at prices ranging > from $11 to $19 US. > > The site is a bit tricky to navigate. I went through > media-->posters--->emotions posters. They also may have a mix-up > involving their Spanish poster. > > If you go through topic-->emotions--->emotions posters you get to > a slightly different page with fewer choices (this drove Marcia > and me crazy until we figured it out). > > Also don't forget to scroll down to see them all. > > The illustrations aren't too clear, but are clear enough to see > that they're quite charming. So if you don't need them as > experimental stimuli, you might want one for your wall. And I'm > not getting a commission for saying that. > > Thanks, Marcia. > > Stephen > > > Stephen Black, Ph.D. tel: (819) 822-9600 ext 2470 > Department of Psychology fax: (819) 822-9661 > Bishop's Universitye-mail: [EMAIL PROTECTED] > Lennoxville, QC > J1M 1Z7 > Canada Department web page at http://www.ubishops.ca/ccc/div/soc/psy >Check out TIPS listserv for teachers of psychology at: >http://www.frostburg.edu/dept/psyc/southerly/tips/ > > > >
RE: The madness continues: the guess mess
I haven't followed this whole thread, but has anyone mentioned the possibility that getting a higher score may not necessarily be a good goal? The purpose of the test is to determine how much a person knows about a content area. If the person guesses and gets it correct, their score incorrectly indicates that they know more than they do. If "guessing success" is normally distributed (as is beginning to emerge in Marc's small sample), the "lucky guessers" will end up with higher scores than the "unlucky guessers" of similar ability. If these scores are used for admissions decisions, and the tests are valid predictors of grad school performance, the "lucky guessers" will be in over their heads and the "unlucky guessers" will not get into better programs that match their abilities. Maybe guessing success isn't distributed normally, but the bottom- line question is: Why do we want to help students get the highest score instead of the score that best reflects their ability? TT Thomas A. Timmerman, Ph.D. Assistant Professor Psychology Department Austin Peay State University Clarksville, TN 37044 931-221-1248 [EMAIL PROTECTED]
Re: The madness continues: the guess mess
Hi I think what is not being emphasized enough in this discussion is that probabilities are expected values for an infinite population; they do not apply to the outcome on any one occasion or even on some finite set of occasions. If someone guesses (in the pure sense), then they will either be lucky, unlucky, or neither on each occasion, depending on the fates (i.e., chance). That is, they might get a higher score, a lower score, or the same score as if they had not guessed. But the overall expectation is of a result producing the same score by either guessing or not guessing (depending on the penalty exacted for guessing). Perhaps whether or not one guesses should be determined by how much of a risk-taker one is? Do you want to chance a lower score in order to have a chance at a higher score? Best wishes Jim James M. Clark (204) 786-9757 Department of Psychology(204) 774-4134 Fax University of Winnipeg 4L05D Winnipeg, Manitoba R3B 2E9 [EMAIL PROTECTED] CANADA http://www.uwinnipeg.ca/~clark
Re: The madness continues: the guess mess
At 07:06 AM 11/6/00 -0800, Diana Kyle wrote: >E's = gain of points. It is possible >ETS structures answers to use each letter the same number of times? If so, >then consistent letter guessing >is not an issue. If not, then the probability of one letter being used >more frequently in answers is >important. How many of us create exams with equal use of all answer >letters? When I use multiple choice items, I do try to balance the letters. BUT, this means balanced over the entire test. So, it is possible that on any subset of 5 items the alternatives would not be evenly distributed. - Marc G. Marc Turner, MEd Lecturer & Head of Computer Operations Department of Psychology Southwest Texas State University San Marcos, TX 78666 phone: (512)245-2526 email: [EMAIL PROTECTED]
Re: The madness continues: the guess mess
As a follow up to my last post, I did ask students in my class to randomly guess at 5 items with 5 possible answers to each. Here are the results: 5 right - 0 4 right - 0 3 right - 0 2 right - 4 1 right - 14 0 right - 9 So, those that guessed correctly on 2 items would have received +.5 (2 right - 1.5 for wrong answers). Those who got 1 item correct would have broken even (0 points). Those that missed all 5 would have lost 1.25 points. So, as I believed, it is possible that some people would have been hurt by guessing. Admittedly a small sample, but if anything it points out that random guessing doesn't ALWAYS help and can in fact hurt a person's score. - Marc PS- TEACHING RELEVANCE! I was able to tie the above data collection in with a discussion of different ways of knowing and how we can turn to empirical methods to examine questions. I didn't do this until after I collected the data though... G. Marc Turner, MEd Lecturer & Head of Computer Operations Department of Psychology Southwest Texas State University San Marcos, TX 78666 phone: (512)245-2526 email: [EMAIL PROTECTED]
Re: lab exam
Dawn, I taught a 1 semester hands-on lab in which we started with a review of basic stats. I put together a simple user-friendly stat review handout. While my students completed a take-home exam, I think an open-book stats exam with the right support materials could be a good option. My theory is that after your intro stat class life is an open-book stat exam. By and large, the exam was a success experience for everybody. Carla Grayson Dawn Blasko wrote: excepted: "For the second exam, I told the students that they would have > a portion of the exam (I'm thinking 20%) in which they would demonstrate > their understanding of design and statistics in the lab in very small > groups. Then I would ask them to upload > a data set to spss, run the appropriate analyses (2-way anova) , print it > and interpret the print out (what effects were significant) what followup > tests to do. >
Re: The madness continues: the guess mess
At 09:40 AM 11/6/00 -0600, Mike Scoles wrote: >Perhaps I am too trusting, but I've got to "guess" that the folks at ETS are >not amateurs at test construction. Favoring some distractors, either by >placement of the correct answer or content of the distractors, is something >that is avoided. So, you are saying that for items it would be possible to eliminate some distractors? If this is the case, then the guessing is not totally random which is a very important point. Namely, if someone's odds of guessing the correct answer improve because the eliminate one or two of the distractors, then guessing is more likely to help. My argument is that with true random guessing, it could hurt someone's score. An example would be that a student has 1 minute left to answer the last 5 questions. Rather than reading and answering 1 question should they guess at all 5 remaining items without even reading the question or distractors. - Marc G. Marc Turner, MEd Lecturer & Head of Computer Operations Department of Psychology Southwest Texas State University San Marcos, TX 78666 phone: (512)245-2526 email: [EMAIL PROTECTED]
Re: moral dilemma?
I think this idea, about stressing students, is a bit mean. It also violates the bond of trust between teachers and students. Look at it this way: Would it pass an IRB? What was the pedagogocal benefit, and did it outweight the cost? Or did it just enable the teacher to engage in a bit of enjoyment of power? A similar protrayal of the use of power: Several years ago, I chanced to give a major test on St. Patrick's Day. As I am Irish myself, I joked that I would give 2 bonus points to anyone wearing all green to the test, and then I forgot I'd said that. On entering the classroom on the 17th I notoced that something was jarringly different. With a shock I realized that the WHOLE ROOM was a sea of green. I called my fellow profs in for a look! Karen K Block wrote: > Dear TIPsters, > I love this antic, but take pause that it may be ethically > questionable. Could you help me decide? > My student, intending to teach the topic of "stress", used an > interesting activity. She had, at the outset of her course told the > students what the ground rules were: so many tests, required > participation, no pop quizzes, etc. On the day allocated to"stress", she > entered the classroom, and in a commandeering way told the students > ..."Today we are having a little quiz""get out one half sheet of > paper, please" Faces dropping, paper tearing, students looking perplexed > and a little unbelieving and a lot betrayed. She used the moment well." > I am going to dictate the quiz question. Please write it down carefully > and then we will have ten minutes to answer. Thank you, and I look > forward to reading your answer." > "Now, she said, Listen Up" (Silence prevailed and tension > mounted). She then spoke the quiz question slowly, very slowly, word by > word, ostensibly so students could write down the question. She said, > slowly and deliberately, so they could take word for word dictation. > "There..is...noquiz." Of > course there was collective relief. And then she could relate their > experience and feelings to "stress." > Now I thought this was rather cool and wish I had thought of it. > But then I realized deception was involved. One of my more conservative > students said,...Suppose one of her students had a heart problem!..And so > I wondered what everyone here thinks inasmuch as this is a thoughtful > bunch re: what one actually says to students and how one interacts with > them under the testiest of conditions at times. > When I took her a bit to task, she averred that this was not her > idea and she had read it in some TIPS-approved publication. Then I > thought perhaps my thinking was just too IRB reactionary and her teaching > behavior was justified given the instructional point. > This is clearly an issue needing collective wisdom. Thanking you > in advance for any true light you might shed on this matter. KB
Re: The madness continues: the guess mess
Although I have no trouble with the logic that says that guessing can't hurt, the assumption is that, if you do not know the answer, guessing will be random with respect to the correct answers. However, it has been my experience that it is not that difficult to create questions for which one incorrect answer is much more likely to be chosen by those who do not "know" the correct answer. Many standardized tests I have seen make use of comon errors in their distractor items. If the Psych test does this, then guessing would not necessarily be the best option, since I assume most guessers will make what appears to them a "best" guess, rather than a random choice. I really do not know if this applies to the test in question, does anyone else? Jeff Nagelbush [EMAIL PROTECTED] Ferris State University _ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com. Share information about yourself, create your own public profile at http://profiles.msn.com.
moral dilemma?
To All: One perspective on this question is that of Institutional Review Boards. Our IRB at Oklahoma State U (on which I sit) evaluates proposals and their risks by asking "Will the subjects encounter the possibility of stress or psychological, social, physical, or legal risks that are greater than those ordinarily encountered in daily life?" By this metric, I would say that your student's demo did not carry risk greater than described in this question. Another aspect of this issue is the implied question of whether we as instructors are obligated to minimize the stress that we put on students. To this I would answer "No." David G. Thomas, Ph.D. Professor and Associate Head Department of Psychology Oklahoma State University (405) 744-7078 [EMAIL PROTECTED] - Forwarded by David G Thomas/psych/cas/Okstate on 11/06/00 09:46 AM - Karen K Block cc: (bcc: David G Thomas/psych/cas/Okstate) 11/03/00 Subject: moral dilemma? 05:12 PM Dear TIPsters, I love this antic, but take pause that it may be ethically questionable. Could you help me decide? My student, intending to teach the topic of "stress", used an interesting activity. She had, at the outset of her course told the students what the ground rules were: so many tests, required participation, no pop quizzes, etc. On the day allocated to"stress", she entered the classroom, and in a commandeering way told the students ..."Today we are having a little quiz""get out one half sheet of paper, please" Faces dropping, paper tearing, students looking perplexed and a little unbelieving and a lot betrayed. She used the moment well." I am going to dictate the quiz question. Please write it down carefully and then we will have ten minutes to answer. Thank you, and I look forward to reading your answer." "Now, she said, Listen Up" (Silence prevailed and tension mounted). She then spoke the quiz question slowly, very slowly, word by word, ostensibly so students could write down the question. She said, slowly and deliberately, so they could take word for word dictation. "There..is...noquiz." Of course there was collective relief. And then she could relate their experience and feelings to "stress." Now I thought this was rather cool and wish I had thought of it. But then I realized deception was involved. One of my more conservative students said,...Suppose one of her students had a heart problem!..And so I wondered what everyone here thinks inasmuch as this is a thoughtful bunch re: what one actually says to students and how one interacts with them under the testiest of conditions at times. When I took her a bit to task, she averred that this was not her idea and she had read it in some TIPS-approved publication. Then I thought perhaps my thinking was just too IRB reactionary and her teaching behavior was justified given the instructional point. This is clearly an issue needing collective wisdom. Thanking you in advance for any true light you might shed on this matter. KB
Re: The madness continues: the guess mess
Perhaps I am too trusting, but I've got to "guess" that the folks at ETS are not amateurs at test construction. Favoring some distractors, either by placement of the correct answer or content of the distractors, is something that is avoided. I cast my vote for Stephen's position. "G. Marc Turner" wrote: > Lucky for us, this is something we can test (no voting required)... Have > your students take out a sheet of paper and randomly guess the answers to 5 > non-existent questions. Each question has a possible answer of a, b, c, d, > or e. Since we want them to truly guess randomly, we will not actually give > them questions... we just want them to randomly give us the responses. > > Here is the key to use to grade the responses: C E D E D > > Now, grade the quizes... if ANY student fails to get at least 1 correct, > the claim that it will NEVER hurt a person's score is false. At this point > we know that Steven's claim does not have support from the data. If you > continue scoring for everyone, you can figure out if my claim of getting 1 > correct, ON AVERAGE has support or not. > > Until we have actual data collected on this, I don't see much point in > guessing as to the benefits or costs of guessing... -- * http://www.coe.uca.edu/psych/scoles/index.html * Mike Scoles *[EMAIL PROTECTED] * * Department of Psychology *voice: (501) 450-5418 * * University of Central Arkansas*fax: (501) 450-5424 * * Conway, AR72035-0001 * * *
Re: The madness continues: the guess mess
Just curious and just getting my coffee fix today. What is the probability our probability data are representative? Haha Seriously now, many students believe if they are going to guess an answer - they should guess the same letter consistently throughout the examination. This strategy should be considered when considering guessing advantage. Using Marc's data collection exercise for example, consistent A's or B's guessed = loss of points, C's = break even - D's or E's = gain of points. It is possible ETS structures answers to use each letter the same number of times? If so, then consistent letter guessing is not an issue. If not, then the probability of one letter being used more frequently in answers is important. How many of us create exams with equal use of all answer letters? My apologies if this has been discussed earlier. Have a great day, Diana Diana J. Kyle, M.A. Psychology Department Fullerton, College Office: 714-992-7166 We are what we repeatedly do. Excellence, then, is not an act, but a habit.- Aristotle The height of your accomplishments will equal the depth of your convictions. --William F. Scolavino - Original Message - From: G. Marc Turner <[EMAIL PROTECTED]> To: TIPS <[EMAIL PROTECTED]> Sent: Monday, November 06, 2000 5:36 AM Subject: Re: The madness continues: the guess mess > Steven is claiming that given 5 questions, with 5 answer alternatives each, > that all students will get at least 1 item correct by random guessing in > ALL situations. This 1 item correct is what is needed when guessing at 5 > items to "break even" with a 1/4 point deduction for wrong answers. > > The claim I'm making is that given the same situation, students will get 1 > item correct ON AVERAGE. This means that, although most students will get > the statistical 1 item correct, others will get more than 1 item correct > and some will get less than one item correct. I do not agree that EVERYONE > will get at least 1 item correct, only some will get this score. My > understanding of probability is that it works ON AVERAGE, not in isolated > cases. So, most students will break even, or even benefit, from guessing, > but some portion of students will actually lower their score by guessing > because they fail to get the 1 item correct. > > Lucky for us, this is something we can test (no voting required)... Have > your students take out a sheet of paper and randomly guess the answers to 5 > non-existent questions. Each question has a possible answer of a, b, c, d, > or e. Since we want them to truly guess randomly, we will not actually give > them questions... we just want them to randomly give us the responses. > > Here is the key to use to grade the responses: C E D E D > > Now, grade the quizes... if ANY student fails to get at least 1 correct, > the claim that it will NEVER hurt a person's score is false. At this point > we know that Steven's claim does not have support from the data. If you > continue scoring for everyone, you can figure out if my claim of getting 1 > correct, ON AVERAGE has support or not. > > Until we have actual data collected on this, I don't see much point in > guessing as to the benefits or costs of guessing... > > - Marc > > G. Marc Turner, MEd > Lecturer & Head of Computer Operations > Department of Psychology > Southwest Texas State University > San Marcos, TX 78666 > phone: (512)245-2526 > email: [EMAIL PROTECTED] >
Night vision (Student question)
Nancy Melucci asks: > >Are there any explanations for variations in the acuity of night vision? Visual sensitivity under low light conditions depends on several factors, all of which might vary among individuals. Dark adaptation (recovery of sensitivity following exposure to bright light) depends on the speed with which the visual pigment rhodopsin is regenerated in the rods. Rhodopsin is formed from vitamin A (which is why severe deficiencies of vitamin A produce deficits in night vision). I don't know whether individual differences in vitamin A would be manifested as differences in quality of night vision - it generally takes a severe deficit to show up as impaired night vision. Any one know whether there are differences in the speed of the regeneration process? Several other factors might vary enough between individuals to create differences in quality of night vision: Clarity of the cornea (people with cataracts will have worse night vision), the lens, or of the viteous humor will determine how much light actually stimulates the retina. Less light transmitted, less to reach the retina to be detected. The size of the pupil when it is fully dilated might vary - the bigger the opening, the more light the eye can gather. Animals that have excellent night vision (like owls) have large eyes and pupils that are capable of great dilation. As we age, we accumulate pigments in the foveal region of the retina (which also reduce our sensitivity to blue light) and these will filter out light and affect vision under low-light conditions. (This has been suggested as the reason why little old ladies like those blue rinses - to them their hair looks white, without them their hair might have a dingy, yellowed cast.) Two other possibilities that are far more speculative: Are there large enough individual differences in amount of convergence among receptors in the periphery to produce differences in sensitivity? There are some variations in the chemical composition of the photopigments for color vision and these have slightly different sensitivity contours (thus, there are different varieties of red-green anomolous color vision, depending on which variant of the red/green photopigment the person has). I suppose it is possible that there might also be variants in rhodopsin, but I don't know of any research on that. Claudia Stanny Claudia J. Stanny, Ph.D.e-mail: [EMAIL PROTECTED] Department of PsychologyPhone: (850) 474 - 3163 University of West Florida FAX:(850) 857 - 6060 Pensacola, FL 32514 - 5751 Web:http://www.uwf.edu/psych/stanny.html
RE: Personality test for counselors [reposted]
[The initial post seems to have been lost in cyberspace. I apologize in advance for the repetition if it reappears.] I would like to broaden this thread a bit by posing several related questions. UWF has a Master's program in counseling psychology, places students in supervised practica, and requires an internship experience in a counseling setting as part of the degree requirements. The questions about screening students for psychopathology raise several important issues: 1. Programs have an ethical and legal obligation to protect the community from harm that might occur from placing a student in a practicum or internship setting when the student is not prepared to function in these environments either in terms of academic preparedness, quality of social skill, and/or presence of psychological dysfunction. What is the best way to go about evaluating students in a program to ensure that the community has been duly protected? Would it be appropriate to include such an evaluation during the admission process? If so, how can this be done reliably? (Our program eventually disbanded attempts at admission interviews because the faculty did not believe these were serving their intended purpose. We now rely on extensive, term-by-term evaluation of students in the program (on all the dimensions noted above) and may decline practicum or internship placements if students don't seem ready. Except for course grades, this evaluation is done subjectively.) 2. A colleague noted that requiring students to undergo therapy as part of their training raises several difficult issues. These include: Who pays for this therapy and/or determines who conducts the therapy? If the faculty act as therapists, problems of dual relations arise (should a practicum or internship supervisor be in the business of conducting therapy with his/her supervisee?). If referals are made to external therapists, problems of confidentiality arise (which will ultimately undermine the usefulness of requiring therapy as a means of protecting the community from harm) as well as other issues such as determining when "enough" therapy has taken place. I have lots of questions and no good answers. What do other programs of this type do? Claudia Stanny Claudia J. Stanny, Ph.D.e-mail: [EMAIL PROTECTED] Department of PsychologyPhone: (850) 474 - 3163 University of West Florida FAX:(850) 857 - 6060 Pensacola, FL 32514 - 5751 Web:http://www.uwf.edu/psych/stanny.html
Re: Night vision (Student question)
What I have read is the opposite - Males appear to have better visual acuity under photopic conditions, while females have lower absolute thresholds under scotopic - and can be seen in childhood. Females also may dark adapt faster. There are other gender differences as well related to acuity. I'm pulling this information from: Coren, Ward, & Enns (1994) Sensation and Perception (4th ed.) At 06:15 AM 11/6/00 -0500, [EMAIL PROTECTED] wrote: Folks, Are there any explanations for variations in the acuity of night vision from person to person (other than owning night vision goggles)? A student asked what the explanation would be, according to her, her brother and husband see better in the dark than she does . I also wonder since this is a subjective and ancedotal account, if night vision has been studied with this in mind (finding out who might have better than average night vision and what neuroanatomical or neurochemical conditions would make this so.) Thanks for any help you can give me. Nancy Melucci Los Angeles Harbor College Deb Dr. Deborah S. Briihl Dept. of Psychology and Counseling Valdosta State University Valdosta, GA 31698 (229) 333-5994 [EMAIL PROTECTED] Well I know these voices must be my soul... Rhyme and Reason - DMB
Re: Night vision (Student question)
Nancy Melucci wrote: > Are there any explanations for variations in the acuity of night > vision from > person to person (other than owning night vision goggles)? See: http://web.utk.edu/~wverplan/biblio10.html for the full article, by William S. Verplanck from University of Tennessee, Knoxville. * "Night Blindness and Nyctalopia. "Some persons report consistent difficulties in seeing at night, even when they are fully dark-adapted. They cannot detect objects readily visible to others and show both confusion and slow recovery after brief exposure to relatively bright light sources. Maneuvering in dimly illuminated spaces and driving or flying at night present serious problems to these individuals. The presence of such a history, whether the disturbance in sight is of recent appearance or long-standing, is usually taken as prima facie evidence of night blindness. "However, a sharp distinction must be made between night blindness as indicated by such reported difficulties and nyctalopia, or true night blindness, which may be diagnosed only on the basis of an accurate measurement of retinal sensitivity. Many, if not most, of those individuals who report difficulty in seeing at night prove to be psychoneurotic. Many who have unusually insensitive retinas, on the other hand, do not report special difficulties in seeing at night, either because they assume that others have the same difficulties, or because they fail to note them in out well-illuminated urban culture, which offers few situations in which intact rod function is required. To establish the presence of nyctalopia, it is essential to use an instrument of established validity for the measurement of retinal sensitivity. "Incidence of Nyctalopia.--No definitive data on the occurrence of nyctalopia in the population are available, since measurements have never been made on a representative sample of the population. From the studies which have been made of selected groups (e.g. school children, service men), it is known that the normal population will include a small percentage of persons of low visual sensitivity whose performance will be as poor as or poorer than that of many individuals whose nyctalopia is associated with disease or degenerative processes. About 2 per cent of the Navy men were disqualified for night duties as "night blind" on this basis. Those so disqualified seldom if ever showed symptoms other than a relatively high absolute terminal threshold, and their reduced sensitivity must be taken as the consequence of the normal variability in the density in the retinal rods and the efficiency of the process whereby rhodopsin, the visual purple, is regenerated. "The incidence of nyctalopia as part of a distinct clinical pattern is not well understood. It has been observed frequently in several diseases, and may appear in certain unusual conditions such as: "(1) Idiopathic Nyctalopia.--Idiopathic nyctalopia is an hereditary absence of rod function, which has been traced through several generations of certain families. Although typically it appears alone, it may be associated with color blindness and myopia. There is no effective treatment. "(2) Oguchi's Disease.--This rare hereditary syndrome, first reported in Japan and later observed in Europe, has its primary symptom nyctalopia with marked contraction of the visual field under low levels of illumination. Ophthalmoscopic examination shows a remarkably gray appearance of this fundus which disappears with dark-adaptation. Day vision is not affected. No treatment as proved of value. "(3) Retinitis Pigmentosa.--Nyctalopia is the first and invariable symptom of retinitis pigmentosa. In the early stages of the disease, dark adaptation takes place, but at a retarded rate. As the disease advances, rod function is progressively lost, and the absolute terminal threshold is elevated. Diagnosis of retinitis pigmentosa is based upon ophthalmoscopic examination. "(4) Glaucoma.--Early impairment and progressive loss of rod sensitivity is observed in glaucoma. "(5) Retinitis Punctata Albescens.--The earliest symptom of this disease is the complete absence of rod function. Often nyctalopia is the only symptom associated with the altered state of the retina. "(6) Other syndromes of the Visual System.--Nyctalopia has been observed as one symptom of each of the following pathologic conditions: myopia, disseminated chorioretinitis, pregnancy, nicotine poisoning, the Lawrence-Moon-Biedl syndrome, gyrate atrophy of the choroid and retina, choroideremia and atrophy of the optic nerve. Nyctalopia may be simulated by opacities of the ocular media. "(7) Overexposure to Sunlight.--Mild transient nyctalopia may appear in persons who have been overexposed to bright sunlight for several days. It will disappear within a few days if the persons will protect their eyes from the sun wither by remaining indoors or by the use of dark sun glasses. "(8) Avitaminotic Nyctalopia.--Epidemics of night blindness hav
Re: The madness continues: the guess mess
Steven is claiming that given 5 questions, with 5 answer alternatives each, that all students will get at least 1 item correct by random guessing in ALL situations. This 1 item correct is what is needed when guessing at 5 items to "break even" with a 1/4 point deduction for wrong answers. The claim I'm making is that given the same situation, students will get 1 item correct ON AVERAGE. This means that, although most students will get the statistical 1 item correct, others will get more than 1 item correct and some will get less than one item correct. I do not agree that EVERYONE will get at least 1 item correct, only some will get this score. My understanding of probability is that it works ON AVERAGE, not in isolated cases. So, most students will break even, or even benefit, from guessing, but some portion of students will actually lower their score by guessing because they fail to get the 1 item correct. Lucky for us, this is something we can test (no voting required)... Have your students take out a sheet of paper and randomly guess the answers to 5 non-existent questions. Each question has a possible answer of a, b, c, d, or e. Since we want them to truly guess randomly, we will not actually give them questions... we just want them to randomly give us the responses. Here is the key to use to grade the responses: C E D E D Now, grade the quizes... if ANY student fails to get at least 1 correct, the claim that it will NEVER hurt a person's score is false. At this point we know that Steven's claim does not have support from the data. If you continue scoring for everyone, you can figure out if my claim of getting 1 correct, ON AVERAGE has support or not. Until we have actual data collected on this, I don't see much point in guessing as to the benefits or costs of guessing... - Marc G. Marc Turner, MEd Lecturer & Head of Computer Operations Department of Psychology Southwest Texas State University San Marcos, TX 78666 phone: (512)245-2526 email: [EMAIL PROTECTED]
lab exam
Hi everyone, I teach a 2-semester 8 credit research methods core. In the first class we learn research methods, review the stats from the previous course, and develop a project to carry out in the second course. One of the goals of the course is to develop teamwork and organizational skills so we do a lot of group work. In the past, individuals have passed the course even though they have done poorly on the exams because they have had partners carry them through the stats and difficult concepts.Then they had a terrible time in the following course. This year I was determined to be sure that each individual had the necessary skills before they go on, so we have lots of tutoring, hands-on labs and homework to go over the critical concepts and stats. I've slowed down and dropped whole chapters to spend more time on key concepts. For the second exam, I told the students that they would have a portion of the exam (I'm thinking 20%) in which they would demonstrate their understanding of design and statistics in the lab in very small groups. The idea was to split my 2 hour lab class into 4 --30 minute periods and have 5-6 students in at a time. Then I would ask them to upload a data set to spss, run the appropriate analyses (2-way anova) , print it and interpret the print out (what effects were significant) what followup tests to do. So here is the question: On the one hand, I've never seen the students work so hard in preparation for this, on the other I fear that about 1/3 of them will fail this section, due in part to lack of understanding and in part to anxiety over the exam format. I hate to destroy the class moral which is already fragile, as they struggle with the complexities of factorial designs. Have any of you done this sort of individual testing? if so, what have you found to work? Thanks for your help-Dawn Dawn G. Blasko Ph.D. Associate Professor of Experimental Psychology Penn State Erie, The Behrend College Station Road Erie, PA 16563-1501 Office phone: 814-898-6081 http://www.pserie.psu.edu/hss/psych/blasko.htm
Night vision (Student question)
Folks, Are there any explanations for variations in the acuity of night vision from person to person (other than owning night vision goggles)? A student asked what the explanation would be, according to her, her brother and husband see better in the dark than she does . I also wonder since this is a subjective and ancedotal account, if night vision has been studied with this in mind (finding out who might have better than average night vision and what neuroanatomical or neurochemical conditions would make this so.) Thanks for any help you can give me. Nancy Melucci Los Angeles Harbor College
Re: The madness continues: the guess mess
You can appeal to authority if you wish but this is not relevant to the mathematical probabilities involved. ETS has its own agendas. I would need to see loads of data to be convinced that it wouldn't hurt a number of students on an individual level to guess on items where they can't eliminated at least two items. You may think me stupid or dense, and perhaps I am, but I would STILL advise high school students taking the SAT to skip on items where they can't eliminate any items, or do something to narrow the range of possible answers. Nancy M.