**0**wrote:

HI, I have got a GWAS summary data with Z-socres and P-values for each SNP, I know that z = logor / seor I am wondering if it is possible to convert Z-scores back to OR values. Thank you!

Question: convert GWAS Zscore back to OR

0

Andy • **0** wrote:

HI, I have got a GWAS summary data with Z-socres and P-values for each SNP, I know that z = logor / seor I am wondering if it is possible to convert Z-scores back to OR values. Thank you!

2

tpoterba • **50** wrote:

You need the OR standard error to do that. Z-scores and p-values only describe your confidence that your estimated odds ratio isn't actually coming from the null. Your p-value is roughly a function of your power to detect a SNP and the effect of that SNP.

If all I know is that I have a p-value of 1e-9, then it's possible that this p-value came from a SNP with a big effect in a small cohort (low power and high effect), or a large effect SNP in a large cohort (high power and low effect). I can't distinguish these two without more information.

Many thanks to your detailed answer!

Z score is often mentioned in GWAS but in fact I am not sure about its defination. You say that "Z-scores and p-values only describe your confidence" Did this mean that Z-score in GWAS is just like z-score being the statistics to normal distribution. How is it associated with z = logor / seor?

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