I have a dataset with missings and I was told by my supervisor to run multiple imputation. This is done. Now I need to calculate Cohen's d effect size for the mean differences between the experimental group and the control group.
According to this link the formula for Cohen's d is quite simple. Further, here is an answer on how to calculate CI for Cohen's d. But how to calculate Cohen's d with CI after multiple imputation?
EXAMPLE
For example, what is Cohen's d with confidence intervals for this data:
Imputation 1
group value
A 2
A 5
A 3
B 4
B 2
B 1
Imputation 2
group value
A 2
A 5
A 2
B 4
B 3
B 1
CALCULATIONS
Imputation 1: Mean difference of is 1
and pooled sd is 1.53
. Cohen's d is 0.65
and confidence intervall is -1.38 to 2.69
.
For imputation 2: mean difference is 0.33
and pooled sd is 1.63
. Cohen's d is 0.20
and confidence intervalls -1.76 to 2.17
.
I am not sure how to use Rubins rule here to get an overall Cohen's d and an overall confidence intervall.