Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

0
votes
1answer
53 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 ...
1
vote
0answers
34 views

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 ...
0
votes
0answers
11 views

Cohen's d with mean absolute deviation

I'd like to use the mean absolute deviation (MAD) in the calculation of an effect size (across 2 groups) that I can then compare to the standard Cohen's d effect sizes (0.2 is small, 0.8 is big). If I ...
0
votes
1answer
49 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_{...
0
votes
0answers
18 views

Cohen's d for 'time' and 'groups' from repeated ANOVA

I have computed partial eta squared (np2) from a two way ANOVA with repeated measures using SPSS. However, I'd like to convert np2 into Cohen's d for time and groups or at least understand a cite ...
1
vote
0answers
54 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 ...
0
votes
0answers
10 views

Reasons for reporting Pearson's r for / alongside standardized mean difference effect size (Cohen's d)

What are the practical use-cases and / or reasons for reporting Pearson's r alongside Cohen's d? This question is a followup to this post where the conversion itself is discussed. Since r calculated ...
1
vote
1answer
202 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 ...
3
votes
1answer
58 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 ...
2
votes
1answer
76 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 ...
2
votes
0answers
33 views

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 ...
1
vote
0answers
48 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 ...
1
vote
1answer
24 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-...
1
vote
1answer
84 views

What is the difference between Cohen's d, ANOVA, and Regression?

It is my undersetanding 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 ...
1
vote
0answers
45 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 ...
0
votes
0answers
47 views

How to statistically compare two effect sizes from the same sample?

I compared group A and B on a number of outcomes and calculated effect size for each outcome (Cohen's d). Rather than saying "effect size for outcome 1 is bigger than outcome 2", I was asked to ...
0
votes
2answers
252 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 ...
0
votes
1answer
16 views

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 ...
4
votes
2answers
595 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 ...
1
vote
0answers
87 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 ...
3
votes
2answers
101 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 ...
0
votes
1answer
441 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 ...
1
vote
0answers
72 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 ...
0
votes
1answer
264 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, ...
1
vote
1answer
64 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 ...
0
votes
1answer
78 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 ...
0
votes
1answer
39 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? <...
1
vote
0answers
70 views

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), ...
0
votes
1answer
29 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 ...
1
vote
1answer
63 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 ...
0
votes
0answers
431 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),...
1
vote
1answer
832 views

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?
0
votes
1answer
177 views

Using transformed data in Cohen's d effect size calculations

I have used a Log10 transformation on my data to transform some non-parametric data to normally distributed so that I could run a Pearsons correlation. Field (2013) states that only problematic ...
1
vote
1answer
458 views

Calculating Cohen's D for a contrast

I have run a t-test contrast by dummy coding three groups. Let's call them A, B, and C. The contrast is A and B against C. Now, I want to calculate an effect size for the resulting t-test. I am not ...
1
vote
1answer
336 views

Sample size calculation for double blind placebo controlled trial

I want to do a double- blind sham controlled clinical trial of a laser therapy for a skin disease. As the primary endpoint is change in inflammation between pre and post treatment/sham biopsies I ...
1
vote
1answer
269 views

How to compute Cohen's d from means difference in T-Score (or Z-Scores) and its CI

I am performing a meta analysis on longitudinal cohort studies reporting outcomes in cognitive performance as a function of adherence to a nutritional variable. Most of them provide "standardized ...
0
votes
1answer
77 views

What does the mean of pairwise differences of two distributions tell use

Pretty naive question here. If we have two paired large (>1000) samples and are interested in a paired Cohen's d then why not take the pairwise difference of the two samples and consider its mean ...
2
votes
1answer
9k views

How to calculate Cohen's D in R [closed]

I want to see if there is a difference in tenure between low performers and high performers. I am using R and I did an ANOVA to test the difference with this code: ...
3
votes
2answers
431 views

Confidence interval for one-sample effect size: effect of uncertainty of variation?

I have a one sample t-test (against null-hypothesis value 0) for which I would like to calculate the confidence interval on Cohen's d. I know the formula for Cohen's d (sample mean minus zero all ...
4
votes
2answers
1k views

Variance of Cohen's $d$ for within subjects designs

Based on this paper by Lakens 2013, I understand there are two recommended ways for calculating Cohen's $d$ for within subjects measures.  Cohen's $d_{rm}$ (which assumes the correlation between ...
1
vote
0answers
60 views

Can a t-test p-value be <.05 when the CI for cohen's d includes zero?

Is it possible for a t-test p-value to be <.05 when the confidence interval for cohen's d includes zero?
0
votes
1answer
165 views

Replication study and Bayes factor

I ran an experiment and got a statistically significant result with an effect size of cohen's d=0.36 (N=20). I decided to run a replication study, this time with 60 participants, and got nothing (d=0....
2
votes
2answers
947 views

Effect size interpretation for Cliff's delta similar to Cohen's “small, medium and large effect”

In 1988 Cohen suggested the following interpretation for effect size: "small~0.20, Medium~0.50, Large~0.80". I'm aware that these values are rather arbitrary and that an extensive disclaimer in this ...
2
votes
0answers
192 views

Variance pooling in Cohen's d

I have a question about the use of pooled variance in Cohen's d effect size metric. Pooled variance assumes both samples are coming from populations of same variance. They quantified this as no one ...
1
vote
0answers
131 views

Conflicting t statistics and effect sizes

Based on Levene tests that were significant at p < 0.001, I'm doing Welch's t-tests on log transformed data with large group sizes (still slightly non-normal). For some reason, the effect sizes I'...
0
votes
1answer
299 views

Help with choosing the correct effect size

I conducted a two-way between groups ANOVA to test the impact of video gaming (gamer/non-gamer) and gender (male/female) on reaction time. I'm conducted my analysis using SPSS and received the ...
0
votes
1answer
161 views

How to treat cohen's d Infinites/NaNs calculated using binary proportions for metanalysis

I am trying to do a metanalysis (using Wilson meta-analysis http://mason.gmu.edu/~dwilsonb/ma.html) comparing the dropout percentage of a treatment with a control group. I tried to calculate the cohen'...
6
votes
2answers
3k views

Do Cohen's d and Hedges' g apply to the Welch t-test?

How do you go about calculating effect size for the Welch t-test?
1
vote
1answer
427 views

How to calculate pre and post treatment Hedge's g effect size to use in meta-analysis of studies with no control group?

How to calculate pre and post treatment Hedge's g effect size to use in a meta-analysis for studies with no control group? Can you do it with just pre and post treatment means and standard deviations ...