Tools for Those Who Summarize the Evidence Base
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Hi everyone,
I just wonder how to convert Mann Whitney U and Kruskal Wallis values into Cohen's d. Any formulas or references you may recommend?
A second question: Is there a way to merge (combine) 2+ subgroup into one group? e.g.
Variabels : Single/Married/divorced...Each has mean+std dev+n
Can I merge single+divorced to get one group ?
Let's say GROUP-1 [SINGLE+divorced] and GROUP-2 [MARRIED]
Sample:
Variable n X s
single 124 1,54 0,63
divorced 65 1,24 0,49
married 132 1,87 0,8
Can it be like ?
Variable n X s
single+divorced 189 1,39 0,56
married 132 1,87 0,8
or can I combine them using weighed average taking n into accaunt?
or first calculate Cohen's d for both groups then get average of two Cohen's ds?
Tags:
Re Question 1: One thought is finding the exact p value for the U or Kruskal-Wallis values and then converting them to a regular t or F and converting that statistic to the SMD (Cohen's d).
Re Question 2: I doubt you get very different results either way, but I usually prefer to combine the means and SDs (appropriately weighted for their sample sizes) and then calculate the SMD. Of course you would pool the relevant SDs. (The old dstat 1 had a handy feature for just that purpose.)
Mr. Johnson
Thank you so much for your assistance.
Blair T. Johnson said:
Re Question 1: One thought is finding the exact p value for the U or Kruskal-Wallis values and then converting them to a regular t or F and converting that statistic to the SMD (Cohen's d).
Re Question 2: I doubt you get very different results either way, but I usually prefer to combine the means and SDs (appropriately weighted for their sample sizes) and then calculate the SMD. Of course you would pool the relevant SDs. (The old dstat 1 had a handy feature for just that purpose.)
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