Re: [HELP NEEDED] What is the best technique to analyze the following experiment?
On 16 Nov 2001 09:34:52 -0800, [EMAIL PROTECTED] (S.) wrote: I performed the following experiment: Each user (U) used several interfaces (I). Both U and I are to be treated as random factors. For each U and I combination, time (T), errors (E) and satisfaction (S) were measured. The data looks something like: U I T E S --- --- --- --- --- U1I1100 1090 U1I2200 2080 U1I3300 3070 U1I4400 4060 U2I1102 1191 U2I2198 1881 U2I5500 5050 U2I6600 6040 . . . etc. Please note that NOT all the users used all the interfaces. The question is: I wish to find the correlations between T, E and S (viz., nullify the effects of U and I). What is the best statistical method of doing this? I think something along the lines of Anova or For the little bit of data shown, the variable *I* has a huge effect, with R-squared of maybe 0.99 with each of the three variables, T, E and S, and that happens while I call it a continuous variable. So it would be just as important, with a waste of degrees of freedom, if it is used as categories; the table shows it coded as categories, I-1 to I-6. High R-squared puts you into the situation where subtle choices of model can make a difference. Is it appropriate to remove the effect of *I* by subtraction, or by division? - by category, or by treating it as continuous? Variance Components should do that trick... I have SPSS, so any advice on how to interpret the output will be most appreciated (please bear in mind that I do not have a degree in statistics). If it is strictly correlation that you want, you can ask for the intercorrelations, while partial ling out the U and I variables. If *I* and U are to be partialled-out as categories, you can create a set of dummy variables, and partial-out those. The result that you get will *not* be robust against scaling variations (linear versus multiplicative, for instance). That is a consequence of the high R-squared and the range of numbers that you have. I suspect that the observed R-squared values might vary in a major way if you just change the raw data by a few points, too -- Note that prediction with an R-squared of 0.99 has *twice* the error of an R-squared of 0.995, and so on; that is approximately the same as the difference between 0.1 and 0.2, in certain, practical consequences. If it will please you to reduce the eventual intercorrelations to zero, a proper strategy *might* be to try alternative models to see if you can produce that result. Of course, in practice, it should be a great deal of help to know what the variables actually, are, and how they are scored, etc., to know what transformations are logical and appropriate. I suspect that data, as stated, leave out some conventional standardization, and so the observed correlations are mainly artifacts. -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html = 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 needed ... :-(
Although this has not much to do with statistics, I agree. With all due respect, being international is much more complicated than being a statistician (or any other professional as a matter of fact). (snip) From the email address, it appears that Dennis lives in a European country where English is not the predominant language. The written English here far surpasses my written French, German or Latin, to mention only languages I have studied. I note that, unlike most Americans, Dennis uses the word "hopefully" correctly. Of course, if Americans were as good with other people's languages as Europeans are, Dennis could have sent us a native-language posting, and then criticized us when we tried to respond in that language. I think this list can benefit greatly from being an INTERNATIONAL list. Let's make folks from other countries feel welcome. _ | | Robert W. Hayden | | Work: Department of Mathematics / | Plymouth State College MSC#29 | | Plymouth, New Hampshire 03264 USA | * | fax (603) 535-2943 /| Home: 82 River Street (use this in the summer) | ) Ashland, NH 03217 L_/ (603) 968-9914 (use this year-round) Map of New[EMAIL PROTECTED] (works year-round) Hampshire http://mathpc04.plymouth.edu (works year-round) The State of New Hampshire takes no responsibility for what this map looks like if you are not using a fixed-width font such as Courier. "Opportunity is missed by most people because it is dressed in overalls and looks like work." --Thomas Edison = 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: Help needed ... :-(
Based on the problems we have in ansering vague questions on edstat, I can say that any requestor must be able to state the question, so we here (using American English) can understand what he is saying and give a helpful answer. It is obvious that all of us have problems understanding the questions in English. The complex field of statistics involves so many variations and such a large body of knowledge, that giving a helpful answer is not easy. I just don't reply in areas that I am weak in. The issue is not on an individual being from Germany, or on international relations, or on responding to people from different cultures and countries, etc., etc. ; the issue is that the requestor should be able to state the question so we can understand it. If he can state the question in German, do it. Requestors post questions in Spanish, Italian, Swedish and in other languages that I can't recognise, and get answers. Let us encourage those on edstat from foreign countries to answer the questions in their own languages and to use their own references. If edstat is to be truely international, we need a lot mre questions and responses in other languages. DAHeiser = 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 needed ... :-(
- Forwarded message from David Heiser - - Original Message - From: Dennis [EMAIL PROTECTED] Hello Newsgroup, I'm searching for real good books on stats. I'm a student of psychology and we've been taught very much stats. But I read all the time your postings and wonder why I've never heard about that what I read. ... Hopefully and with much regards yours Dennis --- What you need is a good class in written English DAH - End of forwarded message from David Heiser - From the email address, it appears that Dennis lives in a European country where English is not the predominant language. The written English here far surpasses my written French, German or Latin, to mention only languages I have studied. I note that, unlike most Americans, Dennis uses the word "hopefully" correctly. Of course, if Americans were as good with other people's languages as Europeans are, Dennis could have sent us a native-language posting, and then criticized us when we tried to respond in that language. I think this list can benefit greatly from being an INTERNATIONAL list. Let's make folks from other countries feel welcome. _ | |Robert W. Hayden | | Work: Department of Mathematics / |Plymouth State College MSC#29 | |Plymouth, New Hampshire 03264 USA | * |fax (603) 535-2943 /| Home: 82 River Street (use this in the summer) | )Ashland, NH 03217 L_/(603) 968-9914 (use this year-round) Map of New[EMAIL PROTECTED] (works year-round) Hampshire http://mathpc04.plymouth.edu (works year-round) The State of New Hampshire takes no responsibility for what this map looks like if you are not using a fixed-width font such as Courier. "Opportunity is missed by most people because it is dressed in overalls and looks like work." --Thomas Edison = 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 needed ... :-(
Well said, Bob -- -- Joe Joe Ward.Health Careers High School 167 East Arrowhead Dr4646 Hamilton Wolfe San Antonio, TX 78228-2402...San Antonio, TX 78229 Phone: 210-433-6575...Phone: 210-617-5400 Fax: 210-433-2828Fax: 210-617-5423 Email: [EMAIL PROTECTED] http://www.ijoa.org/joeward/wardindex.html *** - Original Message - From: "Bob Hayden" [EMAIL PROTECTED] To: "EdStat-L" [EMAIL PROTECTED] Sent: Monday, November 13, 2000 9:46 PM Subject: Re: Help needed ... - Forwarded message from David Heiser - - Original Message - From: Dennis [EMAIL PROTECTED] Hello Newsgroup, I'm searching for real good books on stats. I'm a student of psychology and we've been taught very much stats. But I read all the time your postings and wonder why I've never heard about that what I read. ... Hopefully and with much regards yours Dennis --- What you need is a good class in written English DAH - End of forwarded message from David Heiser - From the email address, it appears that Dennis lives in a European country where English is not the predominant language. The written English here far surpasses my written French, German or Latin, to mention only languages I have studied. I note that, unlike most Americans, Dennis uses the word "hopefully" correctly. Of course, if Americans were as good with other people's languages as Europeans are, Dennis could have sent us a native-language posting, and then criticized us when we tried to respond in that language. I think this list can benefit greatly from being an INTERNATIONAL list. Let's make folks from other countries feel welcome. _ | | Robert W. Hayden | | Work: Department of Mathematics / | Plymouth State College MSC#29 | | Plymouth, New Hampshire 03264 USA | * | fax (603) 535-2943 /| Home: 82 River Street (use this in the summer) | ) Ashland, NH 03217 L_/ (603) 968-9914 (use this year-round) Map of New[EMAIL PROTECTED] (works year-round) Hampshire http://mathpc04.plymouth.edu (works year-round) The State of New Hampshire takes no responsibility for what this map looks like if you are not using a fixed-width font such as Courier. "Opportunity is missed by most people because it is dressed in overalls and looks like work." --Thomas Edison = 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: Help needed ... :-(
Dennis wrote: Hello Newsgroup, I'm searching for real good books on stats. I'm a student of psychology and we've been taught very much stats. But I read all the time your postings and wonder why I've never heard about that what I read. So what I'm searching for is e.g. a profound heuristic, which model or technique is to be used on a specific question of a research or evaluation problem. How important are the assumptions of those techniques. I would guess the main reason that what you read here seems different from what you study is that here the tone is conversational while the tone of a textbook is formal. For the heuristics of linear models, you might look at the linear models book by Neter et al., the linear models book by Kleinbaum et al. (not the epi book) or Regression Analysis by Example by Chattergee and Price. That said, there has been a wealth of books on applied regression analysis published in the last half dozen years. I have not kept up with them but based on the reputations of the authors there are certainly some gems out there. = 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 needed: testing successive regression coefficients
In sci.stat.consult Jason Osborne, Ph.D. [EMAIL PROTECTED] wrote: : I am testing for partial mediation. I need to know whether the : unstandardized regression coefficient for variable X predicting Y in one : regression equation is significantly different from the unstandardized : regression coefficient for variable X predicting Y after a couple : covariates have been entered, in a seperate regression equation. if x is related to the covariates, it's different: trust me, but you don't really want to know that. look at the coefficients and their confidence intervals. that will tell you everything worth knowing.
