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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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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22 views

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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48 views

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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14 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 ...
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23 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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81 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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99 views

Approximating standardized effect-size measures, Cohen's d from glmer model

I'd like to compute the Cohen's d, of glmer model's fixed effects. These are the steps I'm following: Building a model ...
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603 views

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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51 views

Converting Cliffs delta to Cohen's d

I need some help converting effect sizes and calculating 95% CI for these effect sizes. I have a pilot study with 17 participants who completed 4 likert scale measures (Variable 1, Variable 2, ...
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27 views

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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302 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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90 views

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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23 views

Effect size for comparing two groups pearson correlation means

I'm comparing the functional connectivity (pearson r correlation coefficient) between MDD and HC. So I have a matrix of correlation coefficients (pearson r) that correspond to connectivity strength ...
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499 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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300 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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37 views

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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Different conclusions between effect size and seperate population studies

I want to investigate if there are significant differences in the difference of two groups. I have two populations and both populations have a control group and a experiment group. To investigate if ...
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469 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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134 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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73 views

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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661 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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125 views

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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2k views

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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150 views

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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195 views

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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59 views

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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62 views

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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229 views

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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104 views

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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469 views

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 ...
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How do I calculate an effect size (cohens d) from a % difference between interventions and control

If I am basing results on a previous study which has a difference between intervention groups (5 intervention groups) and 1 control of 10.9%. How do I calculate the effect size (d)? I want to be ...
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2k views

Cohen's d from a linear regression model

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 ...
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142 views

Converting Cohen's d to a Relative Risk for a model-based economic evaluation

Hello researchers: my question is about the use of forest plot results for an economic model. In a forest plot you could have the following results: 0.34 [0.22, 0.45], which would be the pooled ...
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204 views

Power calculations using pilot effect sizes

Pilot sample sizes can yield inflated effect size estimates. After conducting a pilot I have found the 95% confidence interval on my effect to have a wide range due to the small sample size. How ...
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835 views

Calculating Cohen's d for pre-post/treatment-control design where treatment-control is also a repeated/within factor

I'm conducting a meta-analysis of studies that used pre-post/treatment-control designs. Most of them are mixed designs (pre-post is repeated/within; treatment-control is independent/between) with a ...
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127 views

Calculating/Averaging/Aggregating Effect Size Across Multiple Measurements

What is the standard practice for calculating a total effect size (using Cohen's d) across multiple measurements in one study? Do you calculate the effect size for each measurement and then take the ...
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426 views

Calculate Cohen's d from mixed repeated messures ANOVA

Can someone calculate Cohen's d for me from these data? F(4, 42) = 39.37, p = 0.001, eta squared = 0.48 There were 3 groups measured on 3 times (pre-treatment, ...
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75 views

Deriving an effect size from previous literature for determining a required sample size for a clinical trial

I'm looking to do a pre-posttest RCT comparing difference of means through a t-test, however I'm completely unsure how to calculate a required sample size using power, confidence level, and ...
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182 views

Is it more accurate to convert t-test statistic to pearson's r or means and SDs to cohen's d to pearson's r when extracting data for a meta-analysis?

I am completing a meta analysis and the common metric I am using is pearson's r. For studies that report comparisons of means rather than correlations should I convert the t-test statistic the author ...
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42 views

Using R: Why I always get different Cohen d values?

Hopefully someone can help me as the question drives me completely crazy. I'm using R to calculate Cohen's d with the following code and every time I get different results. What am doing wrong? <...
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How can Cohen's d < 1.96 ever be statistically significant?

I am having trouble understanding the statistical significance of Cohen's d. My reasoning goes like this: To conclude that experimental group differs from control group significantly (p < 0.05), ...
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36 views

Mini-metanalysis repetead mesures ANOVA 2x2 interaction

I performed two studies on the relation between the stimulus valence (positive/negative) and the action tendencies (approach/avoid) measured with TMS motor evoked potentials technique. For each study ...
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107 views

Cumming's ESCI calculator for within-subjects Cohen's d & 95% CIs

I am calculating Cohen's d and 95% CIs for a within subjects t-test. Cumming's ESCI calculator only estimates the 95% CIs for Cohen's d when df < 200. Is there a theoretical / statistical reason ...
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813 views

Cohen's d / Hedge's g: when to use 'paired' vs 'pooled' method

When calculating Cohen's d or Hedge's g, one can opt to use a paired or pooled method in handling variance. I am working with a small sample size (up to 12 observations in each sample being compared),...
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Can Cohen's d be used for distributions that are not normal?

Can Cohen's d be used for distributions that are not normal? Or is it used only to compare normal distributions?