Statistical Analysis Stack Exchange
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Questions tagged [cohens-d]

Cohen's d is a generalized effect size measure. It is the difference between two group means scaled by the combined standard deviation. Cohen's d is used frequently in Jacob Cohen's text on power analysis, mostly to simplify the presentation of tables.

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Difference between Cohen's d and Hedges' g for effect size metrics

For an effect size analysis, I am noticing that there are differences between Cohen's d, Hedges's g and Hedges' g*. Are these three metrics normally very similar? What would be a case where they would produce different results? Also is it a…
Elpezmuerto
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How do you calculate confidence intervals for Cohen's d?

I've calculated Cohen's d for regression coefficients (from the t statistic), odds ratios and means differences, hoping to pool the results in a meta-analysis and see how it works. However, in Stata, it doesn't seem you're able to pool these results…
user3789
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Variance of Cohen's $d$ statistic

Cohen’s $d$ is one of the most common ways we measure the size of an effect (see Wikipedia). It simply measures the distance between two means in terms of the pooled standard deviation. How can we derive the mathematical formula of variance estimate…
JRK
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Effect size for interaction effect in pre-post treatment-control design

If you choose to analyse a pre-post treatment-control design with a continuous dependent variable using a mixed ANOVA, there are various ways of quantifying the effect of being in the treatment group. The interaction effect is one main option. In…
Jeromy Anglim
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When/why does the central tendency of a resampling simulation markedly differ from the observed value?

Should one always expect the central tendency (i.e., mean and/or median) of a bootstrapped sample to be similar to the observed value? In this particular case I have responses that are distributed exponentially for subjects across two conditions…
russellpierce
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Converting odds ratios to Cohen's d for meta analysis

I'm conducting a meta-analysis largely on mean differences data, however I have several articles that report only an odds ratio, N, p value, and confidence interval, and I need to convert this information to Cohen's d. I am having particular trouble…
Erica
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Alternatives to Cohen's d for non-Gaussian models

Cohen's d (or Hedges' g) are often used to compute effect size. They rely on the assumption of homogeneity of variance across samples however. Because of the pooling of variance that they do, I'm also in doubt that they can be useful in the…
Jehol
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Interpreting effect size

One of the most widely used interpretation of effect size is Cohen's $d$, as follows: $<.10$: trivial $[.10,.30]$: small to medium $[.30,.50]$: medium to large $>.50$: large to very large This appears to be the standard in psychology. I am…
Amarald
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Do Cohen's d and Hedges' g apply to the Welch t-test?

How do you go about calculating effect size for the Welch t-test?
mrchimpbanana
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Understanding the calculation of the independent samples Cohen's d from t & df

It seems that for calculation of Cohen's $d$ (an estimate of effect size), you should use the difference in means (or in one-sample case, from baseline), divided by $SD$, if that information is available: $$ \frac{\bar X_1 - \bar…
Alon
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Effect size and statistical significance

Using Cohen's $d$, I am getting small and medium effect sizes for results that are statistically non-significant ($p>.05$). Does this make sense?
Melissa Duncombe
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Cohen's d for 2x2 interaction

I have a significant 2x2 interaction in a between-subjects design. I would normally report omega-squared as my effect-size measure, but I've been asked to provide Cohen's d instead? Can Cohen's d be computed for an interaction? If so, how?
Bob
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Cohen's d from regression coefficient?

Is it appropriate to calculate Cohen's d (effect size) from the regression coefficient of an independent categorical variable? My coefficient represents participation in an intervention (treatment group = 1; comparison group = 0). My inclination is…
David Bamat
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Can I calculate Cohen's $d$ from multiple regression coefficient?

Question: Is it appropriate to calculate Cohen's $d$ (effect size) from the regression coefficient of an independent categorical variable? Background: My regression coefficient represents participation in an intervention (treatment group = 1;…
user89128
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Statistical comparison of 2 independent Cohen's ds

Is it possible to statistically compare the Cohen's $d$ of two studies in order to determine of one of the two Cohen's $d$s is statistically significantly larger (or smaller) than the other one? I have calculated Cohen's $d$ for two virtually…
user35129
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