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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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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Transformation eta sqaured into cohens d or r

Is there a possibility to convert eta squared to Cohen's d or r? I uded this page (especially calculator 14) to transform different effect sizes into one: https://www.psychometrica.de/effektstaerke....
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Cohen-d issues with pingouin ttest function for paired samples

I have two lists of time values, 'times0' and 'times1'. The data are paired (first value in times0 is paired with first value in times1, second value idem etc etc). I want the cohen-d of the t-test ...
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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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Target population for power analysis of ML model A/B test

We are working on an ML model that predicts a numeric result (call it $\hat{x}$). Eventually, we will perform an A/B test, where the metric is a function that takes $\hat{x}$ as an input (call it $f(\...
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Cohen's d for Longitudinal Data - Between Group Comparison

I am trying to calculate Cohen's d for longitudinal data. Specifically, I want to calculate the effect size for the post-time point between two groups (treatment vs. control). I have built a ...
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Why, in simple terms, is Cohen's D not affected by sample size but a T-Test is?

Why, in simple terms, is Cohen's D not affected by sample size but a T-Test is? I don't really understand and tbh am struggling to tell the difference between the two at all.
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Sample sizes for two independent samples w dichotomous outcomes

I have two groups of very unevenly distributed data, one group has 95% more observations than the other group. My outcome variable is a binary variable. I know how to calculate the effect size, but I'...
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Is it reasonable to calculate a T-test or Cohen's d with one group's sample size, mean and standard deviation being averaged or pooled?

This is my data: year 1: n, mean, sd year 2: n, mean, sd year 3: n, mean, sd year 4: n, mean, sd year 5: no data year 6: n, mean, sd (special event happened) Sample sizes, means and standard ...
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2 outputs when calculating Cohen's d

I've just tried to calculate Cohen's d in R with the following formula: ...
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Using lme.dscore to get Cohen's d

I am performing LME and trying to get Cohen's d for each of my effects. In my data set, I have one fixed factor, “Consistency” (3 levels: con, inc, pro). Subject, Passage, and Stim_set are random ...
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Comparing group differences in within-subject design: Confidence interval around effect size (Cohen d) or with Tukey post-hoc test (after anova)?

I want to compare 4 different conditions of the same task. Dependent variable is “Draws-to-Decision” (number of draws, until a person decides for one of two options). Independent variable is the type ...
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How would I generate an estimate of Cohen's d for an interaction between two effects coded binary predictors in an lmer model?

It doesn't need to be precise, I just need a ballpark. I've found this answer which leads me to believe I can multiply the coefficient by 2 (as the linked post is dealing with dummy coded variables) ...
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Convert correlation r to Cohen's d (unequal groups of known size)

I am doing a meta-analysis. I would like to estimate Cohen's d for various studies. The correlation is made up of (a) a binary variable and (b) a numeric variable. I also know (a) the mean for the ...
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How to compare different effect sizes (d vs. r)?

My question is whether I can compare two different effect sizes (Cohen's d and r). I have tested the differences between two paired groups regarding different variables. They are paired because they ...
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Why is the cohen's d effect-size from this study so different from the value I've computed manually?

In this study [1], they estimate an overall cohen's d effect-size of .70; however, when I try to compute the cohen's d using their means/stds, I get a much smaller effect-size of .47. Am I doing ...
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Two methods of converting Cohen's d to CL (common language effect size / Probability of Superiority) yield different results?

The common language effect size (CLES) of McGraw & Wong, 1992, also known as the probability of superiority, can be conceptualized as the probability that a person picked at random from the ...
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How can I take into account the different sample sizes of the two groups that I am comparing with a t-test or analysis of variance?

I am computing a p-value using the aov function in R in order to detect if the means of two groups are significantly different. However, these two groups that I am ...
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Converting Hazard Rate Ratio and Relative Risk to standardized effect size (eg Cohen's d)

We are 2 psychology students writing a systematic review. We need to convert the effect sizes from the different studies to Cohen's d (or another standardized effect size). Can anyone help converting ...
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Cohen's d and standard deviation from t-test in r

I am looking for how to determine the cohen's d for my t-test so I can make a post-hoc power analysis take the following: the data: ...
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Convert percentile change to Cohen's d

tl;dr: How do I convert from percentile change to Cohen's d for the whole distribution? A common measure of effect size is Cohen's d: the mean difference between an experiment and control group ...
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Comparing coefficient across groups in 3 way linear mixed model

I wonder how to compare coefficients across group in linear mixed model. Dependent variable (DV, continuous variable) is changed by time variable (T, continuous, fixed effect). And hypothesis is that ...
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Confidence intervals of Cohen's d in controlled pre-post trials

The design with two sessions and two groups (treatment and control) is quite common. How can I calculate the confidence intervals for Cohen's d for that design? It is said that in this design we ...
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How to compute Cohen's d when provided percent difference and standard deviation?

I am trying to compute Cohen's d from a published paper. M1 and M2 were provided as percent differences (the average difference in scores from t1 to t2 for an experimental group and then a control ...
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Rubin's rule, applied to absolute effect size or relative effect size (Cohen's d)?

Cohen's d is a way to describe the effect size relative to the standard deviation of the data. For instance in the case of the difference between the means of two populations $$\begin{array}{} \text{...
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What is the formula for the standard error of Cohen's d

I found different answers to the question how to calculate the standard error (SE) of Cohen's d. First formula is (see here, here or here): $$ SE_d = \sqrt{\frac{n_1 + n_2}{n_1 n_2} + \frac{d^2}{2(n_1+...
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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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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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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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1 answer
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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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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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2 votes
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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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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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