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.
180
questions
0
votes
0
answers
17
views
checking normality for longitudinal data
From an experiment where we recorded performances before and after medication, I have gathered data for two groups of patients (Disease A and Disease B) and now I wish to examine if there are any ...
- 21
2
votes
0
answers
35
views
Effect sizes for GLMs
I'm just checking that I understand things correctly. If one wants Cohen's d-style effect sizes, and you have estimates from a GLM -- say a logit model -- there is no such thing--right? Because there ...
- 17.7k
1
vote
0
answers
35
views
Meta-analysis effect size computation
I've been working on a meta-analysis off and on for a while. I am at the analysis stage. Meaning that all relevant effect sizes have been computed. However, I need help understanding what to do when a ...
- 95
1
vote
0
answers
14
views
Meta-analysis for studies with both baseline and follow-up measurements in both control and experimental groups
I am new to meta-analysis. I did a quick search, and I think I can wrap my mind around generating cohen's d and its variance when there is only a single distribution for each of the control group (C) ...
- 281
0
votes
0
answers
51
views
Calculating Cohen's d
I have two groups (experimental and control) and a measure (an estimate of confidence) measured at baseline and at post-intervention. I have ran a multiple regression and found that the intervention ...
- 131
1
vote
1
answer
168
views
What's the appropriate effect size estimate (and power analysis) for post-hoc regression?
I've seen some similar (ex ex2) questions, but hopefully this is not a duplicate. As it is mentioned in one of them, I'm using eemmeans to do pairwise comparisons ...
- 601
1
vote
0
answers
24
views
Can I compare a Cohen's d to a log-response ratio in a meta-analysis?
I'm conducting a meta-analysis and I'm wondering if I can make direct comparisons between different types of effect sizes? For example, can I compare a Cohen's d calculated from one study to a log-...
- 11
0
votes
0
answers
33
views
Calculating Cohen's d from standardized or unstandardized regression coefficients (GLM/GLMM) for meta-analysis
I am currently conducting a meta-analysis about the effect of blood parasites on different fitness parameters of song birds.
Since I have a rather large number of parameters that I want to incorporate,...
- 1
1
vote
1
answer
43
views
How to Simulate T-Values for Two Different Samples
Motivating Question
I had a discussion with somebody recently, who said that a 10 participant sample with a t-value of 2.1 is more impressive than the same t-value for a 100 participant sample. The ...
- 3,885
1
vote
1
answer
30
views
Inter-rater reliability (complex survey )
Help calculating Inter-rater reliability in a complex online survey (free text).
The questions are free text. We have now coded the potential answers. Examples:
1.) Hobbies (Time in nature, mind-body ...
- 11
0
votes
0
answers
55
views
Calculating cohen's D after adding covariates using effect_size package or any package
I have completed optimal full propensity score matching using the Matchit package and now need to re-enter two covariates into my linear outcome regression model. This is because even after matching, ...
1
vote
1
answer
40
views
When calculating a standardized change score, what do you divide by and why?
I understand that, in most cases, one calculates a standardized change between two scores as
(Lakens 2013)
i.e., the mean of the change scores is divided by the standard deviation of the change ...
- 209
1
vote
1
answer
49
views
Cohen's D on transformed data for effect sizes
I have given data for users which is right skewed with a long tail, meaning high gmv is driven by few users. Now I have 2 cohorts of users for whom I want to compare gmv distribution. My first ...
- 143
0
votes
0
answers
24
views
Underlying assumption for calculating cohens D
Is there any underlying assumption when we can reliably use Cohen's D? Do we assume our samples should be Gaussian? I know that Cohen's D is heavily biased by outliers and sample size. But is there ...
- 101
0
votes
1
answer
58
views
Comparing Cohen's D and Arcsine Transformation in Meta-analysis
I'm conducting a meta-analysis that consists of 15 studies and ~40 construct effect sizes. Most of the constructs and studies use continuous variables and were straightforward in finding standardized ...
- 1
1
vote
1
answer
90
views
Converting Cohen's $d$ to Pearson's $r$ $\ne$ calculated Pearson's $r$
I was calculating effect sizes for an analysis and noticed by chance that Pearson's $r$ calculated from Cohen's $d$ with a conversion formula is not the same as when I calculate the correlation given ...
- 35
0
votes
1
answer
37
views
Meta analysis for a number of identical studies (with access to raw data)
I have access to about ten almost identical studies from ten different locations.
They have been done different years, but with the same methodology.
Each site was analysed and reported separately ...
- 53
2
votes
0
answers
59
views
Meta-analysis with rma() in metafor
I am working on a meta-analysis that has two moderator variables. Below is the code that I've figured out, but I'm not sure how to get the forest plot to show the overall model estimate. It's ...
- 95
0
votes
0
answers
33
views
One-sampled t-Test: large Cohen's d and large p value (is there a statisctical error?)
The p-value from a t-test I have run is unexpectedly large, considering Cohen's d.
I calculated the one-sample t-test in RStudio for the following hypothesis:
H2: For athletes who have already reached ...
- 1
1
vote
0
answers
15
views
Effect size and statistical significance correspondence
While I understand that it is possible to have a small effect size with statistical significance and a large effect size without statistical significance, is it ever possible to find this across two ...
- 11
0
votes
0
answers
37
views
Hypothesis testing Cohen's D -> actual difference in means (proportions)?
I'm trying to execute power analysis regarding proportions (successes of trials.) Using Python's stats models package I can specify a number of trials, an alpha and a beta and the MDE returned will be ...
- 2,093
0
votes
0
answers
32
views
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 ...
- 121
1
vote
0
answers
21
views
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, ...
- 11
2
votes
0
answers
40
views
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 ...
- 383
1
vote
0
answers
64
views
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, ...
- 11
0
votes
0
answers
71
views
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 ...
- 23
2
votes
0
answers
667
views
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 ...
- 331
2
votes
1
answer
100
views
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(\...
- 805
1
vote
2
answers
554
views
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.
3
votes
2
answers
445
views
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'...
0
votes
2
answers
53
views
2 outputs when calculating Cohen's d
I've just tried to calculate Cohen's d in R with the following formula:
...
- 1
2
votes
2
answers
550
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 ...
- 43.1k
1
vote
1
answer
219
views
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 ...
Laura
0
votes
0
answers
112
views
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 ...
- 13
3
votes
2
answers
421
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 ...
- 743
0
votes
1
answer
460
views
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 ...
0
votes
1
answer
1k
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 ...
0
votes
0
answers
617
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:
...
- 101
1
vote
0
answers
157
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 ...
- 11
2
votes
2
answers
333
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 ...
- 21
2
votes
0
answers
132
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 ...
user248711
0
votes
1
answer
410
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 ...
0
votes
1
answer
381
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
$$\begin{array}{}
\text{...
- 61.2k
4
votes
1
answer
4k
views
What is the formula for the standard error of Cohen's d
I found different answers to the question how to calculate the standard error (SE) of Cohen's d.
First formula is (see here, here or here):
$$ SE_d = \sqrt{\frac{n_1 + n_2}{n_1 n_2} + \frac{d^2}{2(n_1+...
user248711
2
votes
3
answers
2k
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 ...
- 81
2
votes
1
answer
468
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....
- 331
2
votes
1
answer
2k
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 ...
- 241
3
votes
0
answers
293
views
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 ...
- 295
2
votes
1
answer
345
views
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 ...
- 281
1
vote
0
answers
148
views
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 ...
- 11