# 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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### checking normality for longitudinal data

From an experiment where we recorded performances before and after medication, I have gathered data for two groups of patients (Disease A and Disease B) and now I wish to examine if there are any ...
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### Effect sizes for GLMs

I'm just checking that I understand things correctly. If one wants Cohen's d-style effect sizes, and you have estimates from a GLM -- say a logit model -- there is no such thing--right? Because there ...
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### Meta-analysis effect size computation

I've been working on a meta-analysis off and on for a while. I am at the analysis stage. Meaning that all relevant effect sizes have been computed. However, I need help understanding what to do when a ...
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### Meta-analysis for studies with both baseline and follow-up measurements in both control and experimental groups

I am new to meta-analysis. I did a quick search, and I think I can wrap my mind around generating cohen's d and its variance when there is only a single distribution for each of the control group (C) ...
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### Calculating Cohen's d

I have two groups (experimental and control) and a measure (an estimate of confidence) measured at baseline and at post-intervention. I have ran a multiple regression and found that the intervention ...
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### What's the appropriate effect size estimate (and power analysis) for post-hoc regression?

I've seen some similar (ex ex2) questions, but hopefully this is not a duplicate. As it is mentioned in one of them, I'm using eemmeans to do pairwise comparisons ...
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### Can I compare a Cohen's d to a log-response ratio in a meta-analysis?

I'm conducting a meta-analysis and I'm wondering if I can make direct comparisons between different types of effect sizes? For example, can I compare a Cohen's d calculated from one study to a log-...
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### Calculating Cohen's d from standardized or unstandardized regression coefficients (GLM/GLMM) for meta-analysis

I am currently conducting a meta-analysis about the effect of blood parasites on different fitness parameters of song birds. Since I have a rather large number of parameters that I want to incorporate,...
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### How to Simulate T-Values for Two Different Samples

Motivating Question I had a discussion with somebody recently, who said that a 10 participant sample with a t-value of 2.1 is more impressive than the same t-value for a 100 participant sample. The ...
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### Inter-rater reliability (complex survey )

Help calculating Inter-rater reliability in a complex online survey (free text). The questions are free text. We have now coded the potential answers. Examples: 1.) Hobbies (Time in nature, mind-body ...
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### Calculating cohen's D after adding covariates using effect_size package or any package

I have completed optimal full propensity score matching using the Matchit package and now need to re-enter two covariates into my linear outcome regression model. This is because even after matching, ...
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### When calculating a standardized change score, what do you divide by and why?

I understand that, in most cases, one calculates a standardized change between two scores as (Lakens 2013) i.e., the mean of the change scores is divided by the standard deviation of the change ...
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### Cohen's D on transformed data for effect sizes

I have given data for users which is right skewed with a long tail, meaning high gmv is driven by few users. Now I have 2 cohorts of users for whom I want to compare gmv distribution. My first ...
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### Underlying assumption for calculating cohens D

Is there any underlying assumption when we can reliably use Cohen's D? Do we assume our samples should be Gaussian? I know that Cohen's D is heavily biased by outliers and sample size. But is there ...
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### Comparing Cohen's D and Arcsine Transformation in Meta-analysis

I'm conducting a meta-analysis that consists of 15 studies and ~40 construct effect sizes. Most of the constructs and studies use continuous variables and were straightforward in finding standardized ...
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### Converting Cohen's $d$ to Pearson's $r$ $\ne$ calculated Pearson's $r$

I was calculating effect sizes for an analysis and noticed by chance that Pearson's $r$ calculated from Cohen's $d$ with a conversion formula is not the same as when I calculate the correlation given ...
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### Meta analysis for a number of identical studies (with access to raw data)

I have access to about ten almost identical studies from ten different locations. They have been done different years, but with the same methodology. Each site was analysed and reported separately ...
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### Meta-analysis with rma() in metafor

I am working on a meta-analysis that has two moderator variables. Below is the code that I've figured out, but I'm not sure how to get the forest plot to show the overall model estimate. It's ...
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### One-sampled t-Test: large Cohen's d and large p value (is there a statisctical error?)

The p-value from a t-test I have run is unexpectedly large, considering Cohen's d. I calculated the one-sample t-test in RStudio for the following hypothesis: H2: For athletes who have already reached ...
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### Effect size and statistical significance correspondence

While I understand that it is possible to have a small effect size with statistical significance and a large effect size without statistical significance, is it ever possible to find this across two ...
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### Hypothesis testing Cohen's D -> actual difference in means (proportions)?

I'm trying to execute power analysis regarding proportions (successes of trials.) Using Python's stats models package I can specify a number of trials, an alpha and a beta and the MDE returned will be ...
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### Calculating global and local effects in a multiple regression using Cohen's d

I am calculating the effect size Cohen's d using linear regression. I am looking at the effect of disease on memory, and have also added age, education and sex as confounds to the regression. Cohen's ...
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### common effect sizes in psychological research and calculation/ transformation

I am working on an empirical literature analysis. For that I have to code some variables in a specific manner (analysis includes 150 published studies in the field of behavior Neuroscience, ...
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### How do we call the distribution of a ratio consisting of a constant divided by a truncated normal random variable?

I have been thinking for a while about the following problem of Cohen's d effect size measure $d={\frac {\mu _{1}-\mu _{2}}{\sigma}}$ in random-effects meta-analyses for which I cannot find a more ...
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### Can I calculate Cohen's d (effect size) by hand if I have two means with their SD in a within subjects design?

I have several within-subjects studies that assess more or less the same intervention, but measure the outcome with different outcome measures. Most of my studies display the outcome in mean ± SD, ...
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### Equivalence test to compute no-differences between variables?

I need to state that there is no difference between the outcomes of the two tests (method 1 = fast and simple, method 2 = slow and hard to reproduce). I thought that a non-significant t-test would be ...
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### Converting unstandardised regression coefficients to Cohen's d for meta-analysis

I am conducting a meta-analysis of Cohen's d and some raw effect sizes are unstandardised regression coefficients. Of these unstandardised regression coefficients: Some are based on a binary ...
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