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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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
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How to estimate Cohens D using the independent groups definition but on 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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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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Which effect size measure is appropriate for meta-analysis of pharamcogenetic studies
I have been poked for using cohen's d as an effect size statistic in a meta-analysis of pharmacogenetic studies. Apparently is has been argued that (McGough et al., 2009) cohen's d is not appropriate ...
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240 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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Cohen's d for paired vs. independent samples (and which pooled SD to use for Cohen's d with independent samples)
I have a question for you all about calculating Cohen's d and pooled SDs.
1) one-sample / paired-sample vs. independent samples Cohen's d calculation
It seems that for calculation of Cohen's d (an ...
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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 ~10000 genes between two groups, n=6 samples per group. My pipeline ...
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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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203 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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397 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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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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663 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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950 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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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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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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675 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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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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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 ...
