Re: ANOVA Statistical Significance, where does "d" value come from?

Posted by bdates on Jan 30, 2019; 7:08pm
URL: http://spssx-discussion.165.s1.nabble.com/ANOVA-Statistical-Significance-where-does-d-value-come-from-tp5737341p5737349.html

There's an unlocked copy at http://www.bwgriffin.com/workshop/Sampling%20A%20Cohen%20tables.pdf 

A Power Primer Jacob Cohen Psychological Bulletin [PsycARTICLES]; July 1992; 112, 1; PsycARTICLES pg. 155 - Bryan W. Griffin's Web www.bwgriffin.com Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Created Date: 06/23/05 11:02

Brian Dates

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From: SPSSX(r) Discussion <[hidden email]> on behalf of Michael Palij <[hidden email]>
Sent: Wednesday, January 30, 2019 1:55:03 PM
To: [hidden email]
Subject: Re: ANOVA Statistical Significance, where does "d" value come from?

 

My bad.  When I go to the address I gave I have automatic access to

the article (I guess I get it because I come from the nyu.edu domain but

I don't remember acess being so seamless).  The full reference for the

Cohen article is:

Cohen, J. (1992). A power primer. Psychological Bulletin, 112(1), 155-159.

doi:10.1037/0033-2909.112.1.155

A Google search may turn up an unlocked copy (it is a popular

article with over 32K citations according to Google Scholar).

-Mike Palij

New York University

On Wed, Jan 30, 2019 at 1:11 PM Jon Peck <[hidden email]> wrote:

The Cohen article you cite is under lock and key.

On Wed, Jan 30, 2019 at 10:27 AM Michael Palij <[hidden email]> wrote:

Note that, in general, there are two types of effect size measures:

(1) Percentage of variance accounted for (e.g., eta-square, R-square, etc;

historically, SPSS has peovided only this type of effect size measure).

and

(2) Difference(s) between means (e.g., d, g, f, etc.)

Because of the critical role effect size measures play in statistical power

analysis, one nice reference for effect size measures and power analysis

is Jack Cohen's 1992 article "A Power Primer"; see:

https://psycnet.apa.org/fulltext/1992-37683-001.html

Note2:  For a one-way independent groups ANOVA, Cohen recommends

the effect size measure "f".  However, in your example you only have two

groups (which could have been analyzed by independent groups t-test),

though f can be calculated, d is a simpler and more familiar measure.

Cohen's Table 1 provides a listing of effect size measures, their formulas,

and guidelines for the interpretation of the magnitude of an ES.

HTH.

-Mike Palij

Nrw York University

On Wed, Jan 30, 2019 at 11:01 AM William Peck <[hidden email]> wrote:

5 months into learning SPSS / Statistics and need a hopefully quick primer on one statistic from ANOVA.

I am duplicating a report from last year, which worked great for this year's data. SPSS ran great and I got the output I expected, but need help in interpreting last year's report.

ANOVA output from last year is

Fall CALC1  grades
                        N       Mean            Std. Deviation
Class of 2020   125     2.0720  1.01740
Class of 2021   149     2.6644    .96989
Total                   274     2.3942  1.03320


Fall CALC1 grades
                         SS             df      Mean Square     F       Sig.
Between Groups  23.857  1       23.857  24.252  .000 ***
Within Groups   267.573 272     .984           
Total                   291.431 273                     

*** The footnote on this data says "There is a statistically significant and moderately sized (d = .60) difference in Calculus I grades between 2020 and 2021. "

My question is where do you get "d = .60" (because I don't see it anywhere). If I can find that, at least I'll have a reference for the comment, then I'll study ANOVA myself and post questions as needed.

(The statistician who did last year's report is nowhere to be found ...)

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