Yes, Alpha should always be set a priori, but too many people simply set it arbitrarily at .05 without a priori examination of the important (oops--I almost made the Freudian slip of spelling that last word i-m-p-o-t-e-n-t) factors related to the choice of the alpha level to-be-used. Cheers, Hank
----------------------------------------------------------------------- Hank Goldstein, | HOME: (563) 556-2115 Department of Psychology | FAX: (563) 588-6789 Clarke College | EMAIL: [EMAIL PROTECTED] Dubuque, IA 52001 | HOME: 1835 Cannon St. Office: (563) 588-8111 | Dubuque, IA 52003-7904 ----------------------------------------------------------------------- "There is no cure for birth and death save to enjoy the interval." - George Santayana "The most wasted of all days is one without laughter." - e.e. cummings ----------------------------------------------------------------------- >>> [EMAIL PROTECTED] 11/11/02 12:40 PM >>> Not to really disagree, but there are many ways of increasing power besides increasing sample size. Sample size is often the most expensive/difficult one. Others include more reliable measures, use of more homogenous samples, better control of other (non-subject) extraneous variables (e.g. background noise levels), and measurement and "covarying out" of extraneous variables. On top of that, there's the method of using a strong treatment rather than a weak one. Sometimes students use weak treatments to "be fair", even in what should be exploratory research. There's nothing wrong with using an unrealistically strong treatment to establish an effect, and then weakening the treatment to more realistic levels in later research. I couldn't agree more that setting the alpha level should be done a priori. I don't understand why one would use an alpha level at all if one were going to change it after the data were in. That seems to entirely defeat the purpose of setting a standard. Paul Smith Alverno College Milwaukee -----Original Message----- From: Rick Froman [mailto:RFroman@;jbu.edu] Sent: lundi 11 novembre 2002 11:53 To: Teaching in the Psychological Sciences Subject: RE: Marginally Significant? Although it is true that alpha is somewhat arbitrary, I think to avoid all kinds of mischief, if there is a justification for changing the alpha level, it should be set before the analysis, not post hoc. If you are concerned about making a Type II error, your best choice is to increase the sample size, if possible, instead of raising alpha. Rick Dr. Richard L. Froman Psychology Department John Brown University Siloam Springs, AR 72761 e-mail: [EMAIL PROTECTED] phone and voice mail: (479)524-7295 http://www.jbu.edu/sbs/rfroman.html -----Original Message----- From: Hank Goldstein [mailto:Hank.Goldstein@;clarke.edu] Sent: Monday, November 11, 2002 10:08 AM To: Teaching in the Psychological Sciences Subject: Re: Marginally Significant? Since the choice of alpha is somewhat arbitrary and should depend, to a large extent, on the relative importance (i.e., practical consequences) of Type I and Type II errors, I don't agree that significance is an either-or decision. It may seem that it should be an either-or decision, depending on how simplistic an approach one wants to take to the whole complex concept of hypothesis testing. "Them there" is my 3 cents worth! Warm regards, Hank ----------------------------------------------------------------------- Hank Goldstein, | HOME: (563) 556-2115 Department of Psychology | FAX: (563) 588-6789 Clarke College | EMAIL: [EMAIL PROTECTED] Dubuque, IA 52001 | HOME: 1835 Cannon St. Office: (563) 588-8111 | Dubuque, IA 52003-7904 ----------------------------------------------------------------------- "There is no cure for birth and death save to enjoy the interval." - George Santayana "The most wasted of all days is one without laughter." - e.e. cummings ----------------------------------------------------------------------- >>> [EMAIL PROTECTED] 11/11/02 06:45 AM >>> One of my students doing her senior thesis ran her stats and got results of .056 and .08 for two different ANOVAs. In the past I have seen published ..056 and .08 for two different ANOVAs. In the past I have seen published ..056 and .08 for two different ANOVAs. In the past I have seen ...056 and .08 for two different ANOVAs. In the past I have seen published studies indicating that these are "marginally significant." How do you deal with results of this nature? More importantly, do you have any citations (journals or books) that discuss the value of including/discussing results that seem to "approach significance"? Thanks, Rob Flint ------------------------------------------------------------- Robert W. Flint, Jr., Ph.D. The College of Saint Rose Department of Psychology 432 Western Avenue Albany, NY 12203-1490 Office: 518-458-5379 Lab: 518-454-2102 Fax: 518-458-5446 Behavioral Neuroscience Homepage: http://academic.strose.edu/academic/flintr/ Department of Psychology Homepage: http://academic.strose.edu/academic/psychology/index.htm --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED] --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED] --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED] --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED] --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
