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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Can I calculate effect size using only % difference between means?

I need to calculate the effect size of a published experiment so that I can compare it to a replication attempt. However I have very limited information about the original experiment - only the mean ...
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How do I convert Cramer's V to Cohen's d?

Say I have a chi-squared test that compares 3 different groups: $\chi^2_2 = 9.81$, $p=.012$, Cramer's $V=.33$ How would I go about converting this to a $d$-statistic? Is the proper approach in ...
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1answer
17 views

problem: a sample size for the assumed effect in the 2 sample proportion test

I would like to calculate a sample size for the 2 sample proportion test when the significance level is assumed (0.05), power is assumed (0.90) and I'd like 2 sample proportion test to detect that ...
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1answer
58 views

Cohen's d in proportion test

I am calculating the sample size for proportion test. I would like to have significance level =0.05, power = 0.90 and that the effect size is greater that 5%. I would like to have statistically ...
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9 views

Statistical comparison of 2 dependent cohen's ds

How would I statistically test the significane of the difference between two Cohen's d derived from different tests within the same sample? Specifically, in my neuroimaging data metabolism in brain ...
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72 views

How to convert Spearman's $\rho$, and Cramér's V to Cohen's $d$?

Is there a way to convert both, Spearman's $\rho$, and Cramér's V into the same effect size (f.e. Cohen's $d$), in order to have an information about which of the underlying relationships ...
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34 views

Obtaining Cohen's d from z-test statistic

After an ANOVA, I run post-hoc tests with the glht function in the multcomp package. glht ...
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25 views

simulate ANOVA data to follow a specific eta-squared

I am simulating RM-ANOVA data with three treatment conditions (one-way within subjects designs). I would like to be able to add an effect to the data so that eta-squared has a specific value. ...
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31 views

Identifying formulas from MANOVA in a research paper

I need to identify the formulas for computing the group differences with Bonferroni corrections and Cohen's d effect size in the following paper (chart on the top of page 6): Research Paper What ...
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140 views

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 ...
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76 views

Cohen's d, but using mean absolute deviation

A common measure of effect size used in the social sciences is to look at the standardized difference in means between two conditions (Cohen's d). That is, take the difference in means between two ...
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1answer
318 views

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 ...
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221 views

Cohen d for 2x2 interaction

There is a nice answer to this question, but it assumes that you have the ANOVA table available. My problem is different. Say I'm reading a paper describing a male vs female, disease vs control ...
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1answer
2k views

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 ...
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4answers
255 views

Specific interpretation of non-significant test considering power and effect size

Assuming a test where p > alpha and n is large enough for power > 95% at effect size d, what is the exact interpretation of the test regarding the relationship between the observed data, the real ...
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1answer
330 views

How to combine covariate-adjusted and unadjusted standardised mean differences in meta-analysis?

I have completed an meta-analysis of final scores (comparison of means at post test); however, i have noticed that despite being randomised, differences at baseline are present and are biasing the ...
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180 views

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 ...
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36 views

Concordance test and corresponding plot

I have a list of genes identified using algorithm_A, then using algorithm_B and finally using algorithm_C; then a second list of genes identified using algorithm_A, then using algorithm_B and then ...
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152 views

Given a small pilot study, how to compute number of samples needed for a certain power?

I ran a small pilot study and computed both a p-value and Cohen's d. Now how do I compute the number of samples needed for the full study if I want a given power (e.g. 95%). I hoped I could use this ...
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2answers
364 views

How to estimate Cohen's D using the independent groups definition but on a paired samples data?

I want to calculate cohen's d with confidence intervals for a paired samples designs. Some authors suggest that you use the paired t test value to adjust for the correlation between measures ...
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1answer
260 views

Cohen's d between groups over time question

I have a problem trying to properly phrase my results. I utilized: $$D =\frac{(\text{M}_{2e} –\text{M}_{2c}) – (\text{M}_{1e}-\text{M}_{1c})}{\text{SD}_{1\text{pooled}}}$$ for pooled SD I used: ...
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1answer
578 views

Is a biased or unbiased estimator used for pooled SD in calculating Cohen's d?

When calculating Cohen's $d$ for independent samples, you must use a pooled $SD$. However, I have seen both of these: $$SD_{\text{pooled1}} = \sqrt{\frac{ (n_1 - 1)s_1^2 + (n_2 - 1)s_2^2}{n_1 + ...
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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 ...
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319 views

Does pooled variance correct for/protect from unequal variance when calculating effect size?

This may be a lame question, but I got stuck and can't get my head around it. I am running a gene expression analysis, comparing $\sim 10,000$ genes between two groups, $n=6$ samples per group. My ...
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294 views

How to assess whether two treatments are significantly different using Cohen's d (effect size)?

Cohen's d is a measure of effect size calculated as: $d = (x_1-x_2) / \sigma_{\text{pooled}}$ where $x_1$ is the mean of one group, $x_2$ is the mean of a second group, and $\sigma_{\text{pooled}}$ ...
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3answers
2k views

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?
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347 views

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 ...
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1answer
931 views

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 ...
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1answer
2k views

Cohen's d and multiple comparisons for 2/3-way ANOVA

I am conducting three-way ANOVA (A*B*C) with 2 levels each. 1) I found A*B interaction. 2) I moved to 2-way ANOVA (A*B) and found interaction again. I reported Eta-squared and equivalent Cohen's d. 3) ...
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1answer
1k views

How to calculate Cohen's d effect size intervals for a within-subject design?

I have looked at different web tools for calculating confidence intervals for effect size like Cohen's d for within-subject design. My experience from this survey tells me that there are different ...
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2answers
3k views

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, ...
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3answers
2k views

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. ...
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4k views

How does one calculate Cohen's d and confidence intervals after logit in Stata?

How does one calculate Cohen's d and confidence intervals after logit in Stata?
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1k views

Calculating Orwin's (1983) modified Fail-safe N in a meta-analysis with Odds Ratio as summary statistic?

I am attempting to calculate Orwin's (1983) modification of Rosenthal's (1979) Fail-safe N for my meta-analysis of Odds Ratios. However, all the equations I am finding are using Cohen's d, which I ...
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2k views

How to use Stata to pool Cohen's d?

I am attempting to calculate Cohen's d and then pool those estimates into a summary effect size. Can anyone help? (Stata or SPSS software owned).
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18k views

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 ...