In a matched case-control study or estrogen use and endometrial cancer: Controls Estrogen use + 17 10 Cases Estrogen use + Estrogen use - Estrogen use - 76 111 A.3. Based on these data, what is the crude risk for endometrial cancer and estrogen use, its variance and the 95% CI around it? Where the 95% CI for an OR exp(InOR 1.96*sqrt(var)) So the lower limit= exp(InOR - 1.96*sqrt(var)) And the upper limit= exp(InOR + 1.96*sqrt(var))