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.
Questions tagged [cohens-d]
198 questions
17
votes
2 answers
How do you calculate confidence intervals for Cohen's d?
I've calculated Cohen's d for regression coefficients (from the t statistic), odds ratios and means differences, hoping to pool the results in a meta-analysis and see how it works. However, in Stata, it doesn't seem you're able to pool these results…
user3789
4
votes
1 answer
Cohen's d between groups over time question
I have a problem trying to properly phrase my results.
I utilized:
$$D =\frac{(\text{M}_{2e} –\text{M}_{2c}) – (\text{M}_{1e}-\text{M}_{1c})}{\text{SD}_{1\text{pooled}}}$$
for pooled SD I used:
$$\text{SD}_{1\text{pooled}} = \sqrt{\left((n_1-1)s_1^2…
Robert Price
- 43
1
vote
0 answers
Cohen's d interaction, how to calculate standard deviation
I am working on the review of a manuscript. The reviewer wants effect sizes reported. We have a linear model with an interaction term and we're reporting marginal means for smokers vs non-smokers on another 3 categorical variable.
I decided to use…
SueStat
- 11
0
votes
0 answers
Can I compute Cohen d if the data is both non normal and normal
I am working with the data where some samples follow normal distribution while some do not. How to compute the cohen's d if the data is not normal? As some of data is normal and some is not which effect measure should be used that can cover both…
user395461
0
votes
0 answers
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 any assumption on which it works?
Dexter
- 101
0
votes
2 answers
2 outputs when calculating Cohen's d
I've just tried to calculate Cohen's d in R with the following formula:
mean1 <- mean(Meaningfulness[df$age<=22],na.rm=TRUE)
mean2 <- mean(Meaningfulness[df age>=22],na.rm=TRUE)
sd1 <- sd(Meaningfulness[df$age<=22],na.rm=TRUE)**strong text**
sd2 <-…
0
votes
1 answer
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 raw data is such a way that I work in the…
Xavier
- 23
0
votes
1 answer
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, post-treatment, follow-up; I don't think SD is pooled for any of the SDs). There were…
0
votes
1 answer
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?
library(effsize)
treatment = rnorm(75,mean= 15.37, sd=…
