Re: Joining edstat
On Sat, 28 Apr 2001 [EMAIL PROTECTED] wrote: I just joined the listserv. Our professor is giving us extra credit if we join an email list re: stats. I was able to pull up one of his messages from last year. Pretty cool. Have a great day! You might ask him whether additional extra credit is awarded if you also learn about the usual rules of conduct, sometimes called netiquette. One of them is that persons posting to the listserv are expected to include their proper names at least, preferably accompanied by their affiliations (e.g., college or place of employment or home address, or combinations of these). You might start by visiting the web site mentioned in the trailer automatically appended to this message by edstat. Your e-mail program almost certainly has the facility to include a signature file (sometimes called a .sig) automatically; and even if you think you have valid reason(s) for not doing that as a routine courtesy for all your e-mail, you can easily import such a file into your message for polite communication with listservs and other correspondents, and ought to do so. -- DFB. Donald F. Burrill [EMAIL PROTECTED] 348 Hyde Hall, Plymouth State College, [EMAIL PROTECTED] MSC #29, Plymouth, NH 03264 603-535-2597 184 Nashua Road, Bedford, NH 03110 603-472-3742 = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: errors in journal articles
I think it's a normal situation. Journals have articles with errors. Textbooks have errors. There nothing that can be done, because it's only natural to make mistakes. You should feel good that you can see those things, but be ready that some day they will find an error in your paper. Vadim On 27 Apr 2001, Lise DeShea wrote: List Members: I teach statistics and experimental design at the University of Kentucky, and I give journal articles to my students occasionally with instructions to identify what kind of research was conducted, what the independent and dependent variables were, etc. For my advanced class, I ask them to identify anything that the researcher did incorrectly. As an example, there was an article in a recent issue of an APA journal where the researchers randomly assigned participants to one of six conditions in a 2x3 factorial design. The N wouldn't allow equal cell sizes, and the reported df exceeded N. Yet the article said the researchers ran a two-way fixed-effects ANOVA. One of my students wrote on her homework, It is especially hard to know when you are doing something wrong when journals allow bad examples of research to be published on a regular basis. I'd like to hear what other list members think about this problem and whether there are solutions that would not alienate journal editors. (As a relative new assistant professor, I can't do that or I'll never get published, I'll be denied tenure, and I'll have to go out on the street corners with a sign that says, Will Analyze Data For Food.) Cheers. Lise ~~~ Lise DeShea, Ph.D. Assistant Professor Educational and Counseling Psychology Department University of Kentucky 245 Dickey Hall Lexington KY 40506 Email: [EMAIL PROTECTED] Phone: (859) 257-9884 = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ = = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: poisson process
On Tue, 24 Apr 2001 19:19:02 -0500, burt [EMAIL PROTECTED] wrote: It seems that someplace in my statistical education I read or heard one of my teachers make the following statement: When the occurrence of rare events follows a Poisson process, then a characteristic of this process is as follows: Usually there are long periods of time between the events occurring, but occasionally the event may happen several times in a relatively short period of time. Can anyone provide a reference to this??? The time between occurrences of a Poisson process has an exponential distribution. If you look at a graph of an exponential density function you'll see that there are a few very long time periods between arrivals, and a lot of very short ones. It turns out that those few long periods are sometimes very long periods, so that looking at a time line, if you randomly pick a time, you are likely to pick a time that's within one of those few long periods. A sample sequence marked off on a time line tends to look like xx x x xx x x x x x xxx x The visual appearnce tends to look like what you mgiht expect a non-random clumping process to look like. Pretty much any intro applied stochatic processes textbook should talk about this. Cinlar is one. Ross is another. Gary Carson http://www.garycarson.com = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Help me an idiot
Please help me with my statistics. Question: If you order a burger from McDonald's you have a choice of the following condiments:ketchup, mustard , lettuce. pickles, and mayonnaise. A customer can ask for all thesecondiments or any subset of them when he or she orders a burger. How many different combinations of condiments can be ordered? No condiment at all conts as one combination. Your help is badly needed Just an Idiot@leftover = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: Help me an idiot
On Sat, 28 Apr 2001, Abdul Rahman wrote: Please help me with my statistics. If you order a burger from McDonald's you have a choice of the following condiments: ketchup, mustard , lettuce. pickles, and mayonnaise. A customer can ask for all these condiments or any subset of them when he or she orders a burger. How many different combinations of condiments can be ordered? No condiment at all counts as one combination. Your help is badly needed. Why? All you have to do is construct all the possibilities and count them. Shouldn't be that hard. If you want a method for dealing with more general cases, that might be another matter, of course. But even that would yield to the same procedure, if you went about it in a systematic enough fashion. So how have you approached the problem so far? (I'm a New Englander, and we tend to disapprove of laziness. If you haven't even tried to solve it yourself [and problems like this are almost certainly dealt with in your textbook!], I'm not interested in providing any help at all.) -- DFB. Donald F. Burrill [EMAIL PROTECTED] 348 Hyde Hall, Plymouth State College, [EMAIL PROTECTED] MSC #29, Plymouth, NH 03264 603-535-2597 184 Nashua Road, Bedford, NH 03110 603-472-3742 = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: Help me an idiot
Five different condiments, plus no condiments, means 6*5*4*3*2*1 = 720 distinct combinations. WDA end Abdul Rahman [EMAIL PROTECTED] wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Please help me with my statistics. Question: If you order a burger from McDonald's you have a choice of the following condiments:ketchup, mustard , lettuce. pickles, and mayonnaise. A customer can ask for all thesecondiments or any subset of them when he or she orders a burger. How many different combinations of condiments can be ordered? No condiment at all conts as one combination. Your help is badly needed Just an Idiot@leftover = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: errors in journal articles
The earlier responders make some good points but..I have seen plotted regression lines when the rsquare was 0.005, scatterplots where two populations were separated by a line that makes a southern gerrrymander envious, where clusters had fewer than 3 members, etc. etc. The whole thing would be funny but these journal articles are used to make policy, affect legislation, etc. there is hell to pay if a chemist misreads a spectrum or a geologist confuses east from west. My feelingis that most egregious stuff should be recognized by a comment in the journal. Sending in a comment to a journal is also a good learning experience for the student in that she have to be really sure it is a blooper and that the blooper makes a difference in the conclusions. Lise DeShea wrote: List Members: I teach statistics and experimental design at the University of Kentucky, and I give journal articles to my students occasionally with instructions to identify what kind of research was conducted, what the independent and dependent variables were, etc. For my advanced class, I ask them to identify anything that the researcher did incorrectly. As an example, there was an article in a recent issue of an APA journal where the researchers randomly assigned participants to one of six conditions in a 2x3 factorial design. The N wouldn't allow equal cell sizes, and the reported df exceeded N. Yet the article said the researchers ran a two-way fixed-effects ANOVA. One of my students wrote on her homework, It is especially hard to know when you are doing something wrong when journals allow bad examples of research to be published on a regular basis. I'd like to hear what other list members think about this problem and whether there are solutions that would not alienate journal editors. (As a relative new assistant professor, I can't do that or I'll never get published, I'll be denied tenure, and I'll have to go out on the street corners with a sign that says, Will Analyze Data For Food.) Cheers. Lise ~~~ Lise DeShea, Ph.D. Assistant Professor Educational and Counseling Psychology Department University of Kentucky 245 Dickey Hall Lexington KY 40506 Email: [EMAIL PROTECTED] Phone: (859) 257-9884 = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ = = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: errors in journal articles
In a message dated 4/28/01 2:59:29 PM Pacific Daylight Time, [EMAIL PROTECTED] writes: The earlier responders make some good points but..I have seen plotted regression lines when the rsquare was 0.005, scatterplots where two populations were separated by a line that makes a southern gerrrymander envious, where clusters had fewer than 3 members, etc. etc. The whole thing would be funny but these journal articles are used to make policy, affect legislation, etc. there is hell to pay if a chemist misreads a spectrum or a geologist confuses east from west. My feelingis that most egregious stuff should be recognized by a comment in the journal. Sending in a comment to a journal is also a good learning experience for the student in that she have to be really sure it is a blooper and that the blooper makes a difference in the conclusions. Excellent suggestion provided the journal is willing to print the comments and admit that the article may have errors. This also means the journal has to admit that they missed something when reviewing the article. Just a thought Dr. Robert C. Knodt 4949 Samish Way, #31 Bellingham, WA 98226 [EMAIL PROTECTED] The Law of Gravity says, No fair jumping up without coming down. = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: Help me an idiot
On Sat, 28 Apr 2001 20:35:05 GMT, W. D. Allen Sr. [EMAIL PROTECTED] wrote: Five different condiments, plus no condiments, means 6*5*4*3*2*1 = 720 distinct combinations. WDA Correct me if I am wrong, but aren't you thinking of the number of permutations, i.e., all the condiments plus the no-condiment condition included? When one takes the factorial of a number of items it is the no. of items where the ordering is important. In combinations, the order of ketchup and mustard is not an issue. He could compute the combinations of 5 items, 4 at time, then 3, etc. and add them up plus the no condiment option. To help this kid with his homework, I think a better answer might be somewhere near 32 possible combinations. McDonald's has lots of varieties or so I'm told, but not that many :-))) = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: Help me an idiot
W. D. Allen Sr. [EMAIL PROTECTED] wrote: Five different condiments, plus no condiments, means 6*5*4*3*2*1 = 720 distinct combinations. I wanted that with *fries* and *ketchup*! *Not* ketchup and fries! = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: A disarmingly simple conjecture
On Wed, 18 Apr 2001, Giuseppe Andrea Paleologo wrote: I am dealing with a simple conjecture. Given two generic positive random variables, is it always true that the sum of the quantiles (for a given value p) is greater or equal than the quantile of the sum? snip, technical translation of the question into algebra Any insight or counterexample is greatly appreciated. I am sure this is proved in some textbook, but independently from that, I think this should be doable via elementary methods... If this were a theorem, perhaps it should be. But it does not seem inherently reasonable to me. (Herman Rubin has provided a mathematical response denying the conjecture; but I'd like to look at it from a different perspective. I'd be interested in opinions whether this line of reasoning is valid.) If I understand you correctly, you conjecture that for two random variables (X and Y, say) and their sum (Z, say, = X + Y), the sum of the third quartile of X and the third quartile of Y would be greater than or equal to the third quartile of Z. But this would seem to imply, by symmetry, that the sum of the _first_ quartile of X and the first quartile of Y should be LESS than or equal to the first quartile of Z. There being nothing especially magical about quartiles (whether first, second, or third), these two statements together would imply that the sum of a quantile of X and the corresponding quantile of Y must be BOTH less than or equal to, AND greater than or equal to, the corresponding quantile of Z: that is, the sum of the quantiles must always EQUAL the corresponding quantile of the sum. But for this proposition, I believe there exist lots of counterexamples. -- DFB. Donald F. Burrill [EMAIL PROTECTED] 348 Hyde Hall, Plymouth State College, [EMAIL PROTECTED] MSC #29, Plymouth, NH 03264 603-535-2597 184 Nashua Road, Bedford, NH 03110 603-472-3742 = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
