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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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 [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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13 views

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 ...
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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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How do I get confidence interval for Cohen's D given just the distribution parameters?

I do not have the raw data but I have the Mean Standard deviation Standard error of the mean Standard error of the standard deviation for two groups. How can I compute the confidence intervals for ...
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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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18 views

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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83 views

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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553 views

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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451 views

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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1answer
93 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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242 views

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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33 views

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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147 views

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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579 views

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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98 views

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: ...
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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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155 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 ...
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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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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 $...
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987 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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1k views

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 ...
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812 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 ...
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1k 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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335 views

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 ...
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How can I derive cohen's d from raw data

I hope someone can help me with this simple question: I want to derive Cohen's d from raw data. I know cohen's d is just the (mean1-mean2)/pooledSD. What I want to do is to derive it directly from ...
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Interpretation of two odds ratios derived from two different cohen's ds, comparability for meta-analysis?

I have a question regarding the conversion of cohen's d into odds ratio (OR) and the comparability of results from two different situations. I wonder if the ORs derived from the two situations can ...
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2k views

Cohen's d vs. p-value

I recently started reading Evidence Base Update for Autism Spectrum Disorder. In Table 4 they present a summary of previous work. They use Cohen's $d$ values. From here : $d$ = $|\frac{M_{1} - M_{...
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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 ...