# Calculating Effect Size from Wilcoxon W value (how to get the z value)

Im carrying out a meta-analysis where I have had to carry out my own wilcoxon test on the data. I am now calculating the independant effect sizes for each study to manually input to my excel spreadsheet.

When I have carried out my Wilcoxon test this is my input:

rear<-read.csv(file.choose())
names(rear)
shapiro.test(rear$PI) wilcox.test(rear$PI~rear\$ï..RearingCond)


and my output just provides W = 82, p-value = 0.26

how do i now calculate my effect size and variances for this?

The simplest solution since you have the raw data is to carry out a Student's $$t$$ test and use the mean difference and its standard error from that as your effect size.