# 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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29 views

### 2 outputs when calculating Cohen's d

I've just tried to calculate Cohen's d in R with the following formula: ...
13 views

### 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) ...
41 views

### 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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### What is the consideration to choose cohen d value (0.2, 0.5, or 0.8) to determine the sample size?

I am currently designing the proper sample size in my research about the correlation of two variables. I am using G*Power and using Exact test family and correlation: bivariate normal model ...
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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 , 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 do I use Hedges' g to compare the changes in two groups?

I’m trying to use Hedges’ g in an experiment to compare the change in an intervention group to the change in a control group. I've read through several sources, but I don't know if I have 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 ...
161 views

### 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 ...
126 views

### 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: ...
53 views

### 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 ...
48 views

### 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 ...
56 views

### 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 ...
122 views

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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 ...
158 views

### 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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### 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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### 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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### 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: ...
299 views

### 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 ...
266 views

### 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 ...
553 views

### 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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### Cohen's d in split-plot experiments

There is some demand for effect-size measures in doing post hoc analyses, and I am trying to decide whether to provide for this or not in an R package of mine. If I do, I would concentrate on Cohen's \$...
1k views

### Effect size measure for pretest-posttest design

I recently conducted an intervention study with random assignment to treatment and control conditions. Participants completed a pretest before the intervention and a posttest after. I analyzed test ...
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### How can I compute a confidence interval on Cohen's d derived from a Tukey HSD contrast?

Question Background Consider for example that I have some data arrayed as a 1-way (Group: A, B, C, D) between groups ANOVA. Consider further that I am interested in all possible pairwise contrasts ...
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### Calculate Cohen's d for pairwise tukey tests in a 1-way ANOVA

I have the following dilemma: Design: 1 (Group: Patient vs. Control_1 vs. Control_2) between-factors design arrayed as a 1-way ANOVA Analysis: Following a main effect of group perform I perform all ...
1k views

### How to convert beta from logistic regression into cohen's d?

Is there a way to transform a coefficient from a logistic regression into a cohen's d value? I am trying to calculate the cohen's d for a study with a binary DV while controlling for another ...
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### d to r conversion for extremely high versus extremely low groups

Context Suppose I am performing a meta-analysis on the relationship between two variables (say depression and life satisfaction). Unfortunately, many studies in the prior literature do not report ...
2k views

### Cohens d from Mixed method model - for the interaction term

I am doing a mixed method model: m1 <- lmer(DV ~ IV*Country + (1+IV:Country|Region), data = data) I am using the lme.dscore to get the Cohen's d for the model....
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### Meta-analysis (Metafor) using Cohens D, what is the variance?

I am using the package Metafor in R to do a meta-analysis, my models are derived from lmer (lme4). I am using the package -> EMAtools -> lme.dscore to retrieve the Cohen's d values which will be used ...