PSM Biostatistics Formulas for UPSC CMS: The Complete Reference With Solved PYQs

Key Formulas#

Sensitivity = TP / (TP + FN)
Specificity = TN / (TN + FP)
PPV = TP / (TP + FP)
NPV = TN / (TN + FN)

Relative Risk (RR) = [a/(a+b)] / [c/(c+d)] — incidence in exposed vs unexposed
Odds Ratio (OR) = (a x d) / (b x c) — odds of exposure in cases vs controls

Chi-square = sum((O-E)2/E) — test of independence
t-test = (Mean1 - Mean2) / SE — compare two means