Well, I'd guess you'd say the glass is half empty then. In my research, accounting for any individual differences in language acquisition is hard enough, so I'll take every 1% variance accounted for I can get. I try to convey this attitude when I teach effect sizes. My take on it is that when one starts adding all the 1%s together, pretty soon one get some pretty sweet variance accounted for. And in any case, science doesn't progress by leaps and bounds, it progresses incrementally, over time, when all the little 1%s add up.
I might add that there is a huge push among funding agencies to fund projects with large enough sample sizes to detect small effects; so I guess it's not surprising that there are large N studies and small effect sizes. But I'm not sure I would regard them as automatically lacking clinical significance or meaningfulness; I'm too committed to science as a transgenerational institution to give up on the little bits of variance accounted for that's sprinkled throughout it. Wally Dixon On 8/16/04 5:36 PM, "Paul Okami" <[EMAIL PROTECTED]> wrote: > I suspect that the opposite is far more often the case: Statistically > significant results due only to the fact that large samples were used > represent lack of clinical significance or meaningful group differences. > > Paul > ----- Original Message ----- > From: "Wallace Dixon" <[EMAIL PROTECTED]> > To: "Teaching in the Psychological Sciences" <[EMAIL PROTECTED]> > Sent: Monday, August 16, 2004 5:17 PM > Subject: Re: teaching effect size > > >> Maybe I was too sloppy in my usage. But what I *meant* to say still >> applies. The larger the sample, the smaller the effect size that can be >> detected to be statistically significant. So with extremely large > samples, >> extremely small effect sizes can be detected to be statistically >> significant. But it is not automatically true that small effect sizes due >> to large samples are not meaningful, they can be very meaningful. So, >> people may laugh at you if you say "Hey, I accounted for 1% of the >> variance!" But pragmatically, accounting for 1% of the variance may > benefit >> millions of peoples lives in America alone. >> >> wedj >> >> On 8/16/04 4:38 PM, "Paul Okami" <[EMAIL PROTECTED]> wrote: >> >>> Small effect sizes in large populations are not the same as statistical >>> significance due to large samples. This is what I was referring to. >>> >>> Paul Okami >>> ----- Original Message ----- >>> From: "Wallace Dixon" <[EMAIL PROTECTED]> >>> To: "Teaching in the Psychological Sciences" <[EMAIL PROTECTED]> >>> Sent: Monday, August 16, 2004 12:56 PM >>> Subject: Re: teaching effect size >>> >>> >>>> But you have to be careful about this. As noted by Rosenthal, small >>> effects >>>> sizes in large populations do not mean unimportant. Effect sizes as > small >>>> as 1% can still translate into an influence on millions of people in > the >>> US, >>>> as was the case in the aspirin study and the decreased rate of second >>> heart >>>> attacks. >>>> >>>> Wally Dixon >>>> >>>> >>>> >>>> >>>> On 8/16/04 12:25 PM, "Paul Okami" <[EMAIL PROTECTED]> wrote: >>>> >>>>> I usually give an example of results that are statistically > significant >>>>> because of large samples, but have little meaning in the real world. > In >>>>> other words, they're "real" but "not important." >>>>> >>>>> That makes it easy to talk about a statistic that reflects magnitude > of >>>>> group differences. It's really very intuitive. (I don't discuss the >>> math >>>>> involved). >>>>> >>>>> Paul Okami >>>>> ----- Original Message ----- >>>>> From: "Hatcher, Joe" <[EMAIL PROTECTED]> >>>>> To: "Teaching in the Psychological Sciences" > <[EMAIL PROTECTED]> >>>>> Sent: Monday, August 16, 2004 12:18 PM >>>>> Subject: teaching effect size >>>>> >>>>> >>>>>> Hi Tipsters, >>>>>> >>>>>> I apologize for the cross-posting. >>>>>> >>>>>> I teach the first semester of our two-semester Research Design and >>>>>> Statistics class, my part of which goes through t-tests and requires > a >>>>>> completed project. When I first started teaching the course, "effect >>>>> size" >>>>>> wasn't one of the topics covered. In trying to update the class, I >>> would >>>>>> like to teach this concept, but I'm having some trouble, as it > doesn't >>>>> come >>>>>> as naturally to me as do some of the other topics, and most of the >>>>>> explanations of effect size seem very complicated. >>>>>> Can someone point me to a method to teach effect size that is >>>>> easily >>>>>> understood by undergraduates? >>>>>> >>>>>> Joe Hatcher >>>>>> Ripon College >>>>>> Ripon, WI >>>>>> [EMAIL PROTECTED] >>>>>> >>>>>> >>>>>> >>>>>> Joe W. Hatcher, Jr., Ph.D. >>>>>> Psychology >>>>>> Ripon College >>>>>> Ripon, WI 54971 >>>>>> USA >>>>>> [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] >>>>> >>>> >>>> >> >>> ------------------------------------------------------------------------- > - >>> -- >>>> Wallace E. Dixon, Jr. | >>>> Chair and Associate Professor | If children grew up according > to >>>> of Psychology | early indications, we should > have >>>> Department of Psychology | nothing but geniuses. >>>> East Tennessee State University | -Johann Wolfgang von Goethe >>>> Johnson City, TN 36714 | >>>> (423) 439-6656 | >> >>> ------------------------------------------------------------------------- > - >>> -- >>>> >>>> >>>> >>>> >>>> --- >>>> 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] >>> >> >> >> -------------------------------------------------------------------------- > -- >> Wallace E. Dixon, Jr. | >> Chair and Associate Professor | "When I turned two I was really >> of Psychology | anxious because I'd doubled my >> Department of Psychology | age in a year." >> East Tennessee State University | -Steven Wright >> Johnson City, TN 36714 | >> (423) 439-6656 | >> -------------------------------------------------------------------------- > -- >> >> >> --- >> 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]
