Formula for Cohen's d 95% CI using estimated marginal means

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by Francisco » Sat Dec 12, 2020 6:38 am


I was conducting an ANCOVA using a fixed factor with two groups, a continuous dependent variable, and a continous covariate, and was interested in calculating an effect size and its 95% confidence interval (CI) using the marginal means. I noticed that JAMOVI has an option to calculate a Cohen's d and the 95% CI using the estimated marginal means but the CI provided differs from the one I calculated manually. Is there anyway of knowing what specific formula JAMOVI is using to conduct Cohen's d and the 95% CI using estimated marginal means? Also, Is it calculated using the standard error for the estimated marginal means?


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by jonathon » Sat Dec 12, 2020 6:49 am

hi francisco,

jamovi makes use of the eff_size() function from the emmeans package to calculate these:


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