# Alon

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 Jan18 awarded Notable Question Oct21 awarded Popular Question Jun21 comment Is a biased or unbiased estimator used for pooled SD in calculating Cohen's d? Thank you for pointing that out, Michael. The post above by Matt Krause confirms this. And so it would seem that for small sample sizes, Hedges' g should be used, since it provides a better estimate in that case. Is that reasonable? Jun21 comment Is a biased or unbiased estimator used for pooled SD in calculating Cohen's d? Thanks for editing my question so the formatting is much more clear, Jeromy. Jun14 asked Is a biased or unbiased estimator used for pooled SD in calculating Cohen's d? Jun14 comment Cohen's d for paired vs. independent samples (and which pooled SD to use for Cohen's d with independent samples) OK great! So to calculate d from t for independent groups, you must change SDeffect in the denominator of t to SDpooled. Since SDeffect = 2*SDpooled (assuming no correlation) as you eloquently explained above, you must add a "2" to the numerator as well. So why does d use SDpooled rather than SDeffect as t does? Are we putting the difference in means into units of either group, instead of into units of the effect? And would the argument to use pooled variance for paired samples be that how much the two paired samples correlate would vary and so is not a consistent measure? Thanks! Jun14 awarded Supporter Jun14 awarded Editor Jun14 revised Cohen's d for paired vs. independent samples (and which pooled SD to use for Cohen's d with independent samples) deleted 896 characters in body Jun14 comment Cohen's d for paired vs. independent samples (and which pooled SD to use for Cohen's d with independent samples) Hey John, you make a good point. I appreciate your in-depth answer to the first part, and I'll post the second part as a separate question soon, and take it out of the post, as well. Jun14 awarded Scholar Jun14 accepted Cohen's d for paired vs. independent samples (and which pooled SD to use for Cohen's d with independent samples) Jun11 awarded Student Jun11 asked Cohen's d for paired vs. independent samples (and which pooled SD to use for Cohen's d with independent samples)