Only in two extreme cases, the chi-square approximation holds, when \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$Z_{{\mathrm{eQTL}}} \gg Z_{{\mathrm{GWAS}}}$$\end{document}ZeQTL≫ZGWAS or \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$Z_{{\mathrm{eQTL}}} \ll Z_{{\mathrm{GWAS}}}$$\end{document}ZeQTL≪ZGWAS. In these extremes, we can apply Taylor expansions to find an interpretable form of the SMR statistic.
