Like any other test, using only the Shapiro-Wilk p-value is sometimes useless., especially with a large sample size ...

I did some searches and didn't find any suggested way to calculate the SW effect size. (and interpretation)

Usually, the direction is to run the SW test (or other) and estimate the effect size by the QQ plot. (a subjective way ...)

Do you know any suggested way to calculate the effect size? (the effect size of the deviation from normality )

If not, I thought about something like running a linear regression over the QQ-plot data, and calculate the effect using the R squared

Effect = 1- R-Squared

Thanks,

PS I know some wise people think it is useless...

But I IMOHs effect size will add some contribution, at least some times

http://www.talkstats.com/threads/pl...ata-and-checking-normality.76403/#post-225257