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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Help with choosing the correct effect size

I conducted a two-way between groups ANOVA to test the impact of video gaming (gamer/non-gamer) and gender (male/female) on reaction time. I'm conducted my analysis using SPSS and received the ...
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26 views

Cohen's d in pre-post meta analysis based on means and SD

As follow up on this question:I want to incooporate studies using different continues outcome in a meta analysis using SMD. I am following this guide and I do not fully understand how to calculate the ...
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34 views

How to treat cohen's d Infinites/NaNs calculated using binary proportions for metanalysis

I am trying to do a metanalysis (using Wilson meta-analysis http://mason.gmu.edu/~dwilsonb/ma.html) comparing the dropout percentage of a treatment with a control group. I tried to calculate the cohen'...
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Pearson's r and Cohen's d

I am analyzing the relationship between 3 variables (identification rate (ID) of students with disabilities, per pupil expenditures (PPE), and graduation rate (GR)) in the following format: 1. ID - ...
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11 views

Can I extrapolate a mean difference from the t-statistic?

I have the t-statistic, df, p and cohen's d for the one-tailed independent samples t-tests on the difference between a parameter for cases and controls. I would like to obtain a mean difference and ...
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41 views

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?
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45 views

How to calculate pre and post treatment Hedge's g effect size to use in meta-analysis of studies with no control group?

How to calculate pre and post treatment Hedge's g effect size to use in a meta-analysis for studies with no control group? Can you do it with just pre and post treatment means and standard deviations ...
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1answer
36 views

How to calculate cohen's d (and CI) for survey data

I am working with the TIMMS and PIRLS data. Both data sets use a Jackknife repeated replication design. Both data sets also use 5 plausible values for each student's grade (5 values with different ...
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30 views

Bayes factor for effect size

I need to construct Bayes Factor for testing: $$ H_0: \quad 0 = \mu_t - \mu_c $$ $$ H_1: \quad 0 \neq \mu_t - \mu_c $$ and my prior knowledge is modeled by distribution of effect size: $ \delta = \...
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54 views

Cohen's d for unequal variance

I know my two samples have unequal variance. Should I consider this in my calculation of the effect size? I'm using Cohen's d, which Wikipedia defines as $d = \frac{\bar{x}_1 - \bar{x}_2}{s}$ with ...
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61 views

Is it possible to calculate cohen's d from nonparametric statistics?

I am working on my thesis and my supervisor wanted me to calculate cohen's d for my significant results. I am using SPSS and I was able to calculate Cohen's d using an external site. My independent ...
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125 views

Pooled Variance for Dependent $t$-test statistic?

I'm looking into finding a way to calculate Cohen's $d$ for correlated samples. Assuming pooled variances, we end up getting $$\text{SE}\left( \Delta \text{ of means}\right) = S_p\sqrt{\dfrac{1}{n_1}...
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60 views

Effect size (cohen's d) when mean and SD are zero

I am calculating effect sizes (Cohen's d) for a meta-analysis to examine pre-test to post-test differences after receiving a word-learning treatment. I am using pre-test and post-test means and SDs in ...
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56 views

Effect Size PDF (and Confidence Intervals)

I've already read this, which isn't very helpful. Consider Cohen's $d$ for two independent random samples $\{X_{1j}\}_{j=1}^{n_1=N}, \{X_{2j}\}_{j=1}^{n_2 = N}$, given by $$d = \dfrac{\bar{X}_1 - \...
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34 views

Cohen's d interaction, how to calculate standard deviation

I am working on the review of a manuscript. The reviewer wants effect sizes reported. We have a linear model with an interaction term and we're reporting marginal means for smokers vs non-smokers on ...
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54 views

Generalized eta squared or Cohen's d with trimmed means

For my analysis I am currently running a 1-way within-subjects bootstrapped ANOVA with trimmed means (rmanovab from Rand Wilcox's ...
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53 views

Comparing effect sizes across different data sets with non-normal data

I want to conduct a comparative analysis across a large amount of studies by looking at the effect sizes of their results with another variable. I am not too familiar with effect sizes so I'd ...
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67 views

Transforming Cohen's d effect sizes into unit changes

I want to calculate unit changes (or percentile changes) from an intervention for a continuous outcome variable where I have the pre and post test means and standard deviations. From that I can ...
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162 views

Cohen's d for 2x2 anova interaction [duplicate]

I would like to calculate Cohen's d for 2x2 ANOVA interaction (nationality: Germany, France; gender: male, female). Someone asked similar question earlier (Cohen's d for 2x2 interaction), and ...
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38 views

How to include Cohen's D from Meta-Analysis into JAGS/BUGS mean difference model

I was wondering if anyone knew of a way to use Cohen's D (and Standard Error) as an informed prior while building a BUGS model (to be tested in JAGS through R) that compares the mean difference ...
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138 views

Effect size of a binomial test and its relation to other measures of effect size

I would like to find the effect size of a binomial test and relate it to other measures of effect size such as Cohen’s d or Pearson’s r. Say I have 13 successes for 18 trials, where the probability ...
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248 views

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 ...
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131 views

Calculate cohen's d from multiple 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 ...
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103 views

Is the Cohen's D a suitable test for my dataset?

I have two variables (A and B). A has 3,000 samples; B ...
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108 views

Cohens d effect sizes

I'm using Cohens d effect sizes as a means of providing a magnitude based inference in a study I'm conducting. I just wanted to clarify if I'm correct here: Anything between .0 and .2 is small. ...
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50 views

How to compare latent mean difference from Measurement Invariance with cohen's d from a meta-analysis?

I was wondering if it is possible to compare latent mean differences estimated in a scalar invariance model to an overall Cohen's d found in a meta-analysis. Is there a way to convert one value to the ...
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87 views

Can I use a partial eta squared on t-test results?

I am currently trying to decide which effect size is the most appropriate for my results. I have conducted a repeated measures ANOVA, there are five variables in the ANOVA, all of which are within ...
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50 views

Cohen's d calculation in R

I am using following code to find Cohen's d (means are m1 and m2, standard deviations are s1 and s2 while sample sizes are n1 and n2): ...
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249 views

Cohen's D: Should I use raw data, log transformed data or back transformed data?

I am a doctor and right now I am doing medical research. I have some questions about cohen's d. I try to research it on the internet but it seems there is not much answer to this question. My project ...
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94 views

Calculating effect sizes without SDs or sample sizes for meta-analysis

I'm coding articles for a meta-analysis looking at group differences on dichotomous and continuous outcomes. Groups are not the same size. Continuous outcome ES is standardized mean difference and ...
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41 views

Unit weighting for linear composites / regression

Cohen (1990) mentions a regression that I have not heard about before. Here is how I understand his description: Standardize the dependent and the independent variables Regress the standardized ...
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71 views

Where does this formula for calculating pooled standard deviation for calculating Cohen's d come from?

On this page, it is said that the pooled standard deviation for calculating Cohen's $d$ can be calculated as $\displaystyle SD_{pooled} = \sqrt{\frac{SD_{1}^{2}+SD_{2}^{2}}{2}}$. Where does this ...
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381 views

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 ...
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Cohen's d in non-significant results

I did several independend t-tests. Some of them are significant, some of them are not. Next, I computed Cohens $d$ for effect size. For significant results, Cohens $d$ feels intuitively reasonable ...
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588 views

Why is the p-value for Cohen's $d$ not equal to the p-value of a t-test?

I am using the package compute.es in R to calculate effect size from a $t$-test. The $t$-test is marginally significant with $p=0.05657$. When I run ...
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95 views

Computing sample sizes from confidence intervals around Cohen's d

Is there a way how to compute sample size from Cohen's d and 95% confidence intervals (it's useful for instance for getting sample sizes from forest plots)? From How do you calculate confidence ...
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240 views

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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73 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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521 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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109 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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208 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 (nominal&...
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52 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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58 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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180 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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158 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
1k 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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413 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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4k 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
373 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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765 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 ...