# 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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### How to interpret a large Cohen's d when p-value is non-significant and CI's are close to 0

I have a sample size of 23, with 11 and 12 participants in each group. I conducted t-tests for several continuous dependent variables. All of them are non-significant, but some of them have quite high ...
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### How to convert a negative binomial regression coefficient to an alternative effect size?

I am conducting a meta-analysis and the effect sizes are mostly Cohen's d or log odds ratios. However, a few of the effect sizes are regression coefficients obtained from negative binomial regressions....
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### Is the squared Cohen's $f$ the same as Cohen's $f^2$?

Question Is the squared version of Cohen's $f$ the same as Cohen's $f^2$? Or do they only share the same letter by coincidence? Explanation At first, I wondered if one can simply square Cohen's $f$ to ...
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### Calculating Cohen's d with confidence intervals (CI) after multiple imputation

I have a dataset with missings and I was told by my supervisor to run multiple imputation. This is done. Now I need to calculate Cohen's d effect size for the mean differences between the experimental ...
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### How to calculate Cohen's d between multilevel model predictions at two points in the domain?

I would like to get a Cohen's d between model predictions at different points in the domain of a mixed effects model. I have model predictions and I have bootstrapped standard errors. I mention the ...
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### Cohen's $d$ after linear regression

Assume the model: $$Y = \beta_0 + \beta_1x_1 + \beta_2x_2 + \varepsilon$$ Where $x_1$ is a continuous variable of no interest and $x_2$ is a group variable (0/1). I would like to estimate the effect ...
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### How to interpret hedge's g and how to handle p-value in this context for a sensor measurement/comparison?

It might be that this question has been handled already but there are so many about hedge's g I cannot walk through all of them. Please excuse if it is a duplicated question. I would like to know ...
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### standardized mean difference including between and within subject designs

I am in the process of drafting a meta-analysis for a research project. The document makes use of a forest plot (random-effects model) that depicts the standardized mean difference of each study along ...
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### Determine effect size through correlation with third variable

I am trying to estimate the size (Cohen's D) of the effect of variable A on variable B. Variable A is a condition variable with two levels (treatment versus control). Variable B is a continuous ...
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### Finding effect size from a research paper

I am writing a review paper under a prof this summer, and I'm desperate to demonstrate that I am competent, despite being as inexperienced and unqualified as possible. I am working on a compiling the ...
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### Statistical comparison for large sample sizes (n>1000)

I am comparing the drug exposures across two different groups, consisting of 1000 simulated drug exposures per group. Drug exposures are continuous variables following a normal distribution. I want to ...
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### Calculating variance of one-sample cohen's d effect size

I'm trying to perform a meta-analysis where my effects are mainly one-sample t-test against chance level. I've easily found the one-sample cohen's d formula but I'm not able to find the variance ...
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### Difference between Cohen's d and beta coefficient in a standardized regression model with dummy coded predictor variable

I have been wondering about this for a while now and I just could not find an answer to it, so I'd be glad if someone here could help me out! If I have a simple regression model with a standardized ...
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### Would it be appropriate to use Cohen's ds to evaluate the effect size in a negative binomial model?

I am working on a research project that involves the use of a zero-inflated negative binomial model. In the model I have included the interaction term between a binary and continuous predictor. The ...
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### How do you calculate cohen's L so that you can plug it into a power calculation for multiple linear regression?

I am reviewing a book called Statistical Methods for Healthcare Research so I can learn how to do a power calculation for my sample size for multiple linear regression. This book says that cohen ...
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### What is the intuition behind Cohen's d?

Can anyone please help me in understanding what does the result of Cohen's d gives us? Like how do we interpret the results and what does the positive and negative sign mean?
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### Cohens d effect size calculations across 3 groups

Is it possible to calculate a single Cohens d effect size, across 3 groups? I have successfully used Cohens d to calculate the effect sizes between state 1 and 2 (as simple example given below) for ...
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### Compare/Interpret t-statistics

I've a table as the following that contains the results of one sample t-test on four independent collections for the null hypothesis that the mean is 0: ...
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### Wrong sign for cohen.d {psych} in R?

I'm trying to calculate Cohen's d with cohen.d from the {psych} package in R. So this is the descriptives output (means of variables for groups): ...
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### Converting Hedges' g to Cohen's d, Cohen's f or r?

Is there a sensible way to convert a Hedges' g (effect size) value to Cohen's d, Cohen's f, or r? I've read here that one can convert between d and r, and I know that Cohen's d and Hedges g are very ...
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### How should I calculate sample size when Cohen's $d$ effect size is $> 5.6$?

I am working in R. I am doing some simulations of sample sizes by drawing random samples from two normal distributions. I am calculating Cohen's $d$ effect size with: ...
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### Two different versions of Cohen's D? Which one to use?

I am trying to measure the effect size of some variables between two different groups. I've taken some python code from a few tutorials, but they seem to be calculating it in different ways. I ...
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### Compute standardized mean difference and its standard error from regression-adjusted mean and 95% CI for 2 groups

I am working on a meta-analysis (using aggregated data), where the outcome is a continuous variable. One study reported post-treatment outcome values as regression-adjusted mean and 95% CI in each of ...
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### Independent t-test with multiple imputation including pooled effect size (R, mice)

I just started using multiple imputation in R using the mice package. I want to conduct an independent t-test on the imputed data. Here's a minimal working example:...
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### When to use Cohen's d and when t-test?

When do I use Cohen's and when do I t-test? Probably in addition: What is the (conceptual) difference between them? Both tests are meant to study the difference between two distributions. I just ...
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### Can the r-scale value (for Bayes Factor) be directly based on Cohen's d?

I want to set an r-scale value for a Bayesian t-test (i.e. to calculate Bayes Factor likelihood ratio) based on previous results (i.e., from a posterior). But I simply cannot find a straightforward ...
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### Converting between correlation and effect size (Cohen's d)

Several sources (here here here) claim that there is a relation between Cohen's d and Pearson's r if the data is paired (bivariate). This strikes me as odd since, for example, evaluating a "before and ...
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### Meta-analysis with response ratio effect size

I am interested in comparing the performance of two different techniques (i.e., Method A vs. Method B) on a continuous outcome of interest. The performance of such techniques is measured through test ...
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### Meta analysis Cliff's delta

Cliff's delta is an effect size typically recommended whenever the normality and homogeneity assumption do not hold---and thus, Cohen's d cannot be used. However, I cannot see any reference ...
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### Are effect sizes on different populations comparable?

Does it make sense to conclude that an effect is (likely) stronger in population A than in population B because the effect size estimated on A is larger than that estimated on B? (The samples are not ...
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### Cohen's d and Sten scores

Can someone explain why Cohen's d of sten score is 2 times of Cohen's d of SD? Thanks. The question is based on the paragraph below: *When looking at differences it is useful to remind ourselves of ...
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### Network meta analysis without standard deviations

I am trying to compute Cohen's in some studies that I gathered in a Systematic Literature Review. Unfortunately, almost none of them report the standard deviation (nor df/t, or something for back-...
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### What is the difference between Cohen's d, ANOVA, and Regression?

It is my understanding that ANOVA, Regression, and Cohen's d each measures the distance between means of two or more groups. If that were the case, then what is the purpose of having different methods ...
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### How to compare two age distributions in a population of people?

I have data on a number of clubs and the ages of their members broken down into categories from 0 to 94 and then a final category of 95+. I have about 10,000 clubs and I need to compare how similar ...
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### Cohen's d calculation when within group variance is zero

We have a single-case experimental design and we calculated Cohen's d for effect size using the mean difference between pre and post, divided by pooled standard deviation. However, for one of the ...
Problem: I have a multiple regression model with categorical/binary ($c_i$) and continuous ($x_i$) variables: $v = \alpha + \beta_1 x_1 + \beta_2 x_2 + ... + \gamma_1 c_1 + \gamma_2 c_2 +$ I am ...