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Cohen's d

Cohen's d is the widely used standardized ES we've encountered many times already. The idea that d is a number of SDs is fairly simple, but in practice there can be tricky choices to make. I suspect that most researchers don't appreciate the wide range of measures that appear in journals with the label “d.” The first decision is the choice of SD to use for the standardization, and then you need to decide whether to adjust d to remove bias. It's essential to think carefully about the choices, then state clearly how you calculate the ...

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