= . This is derived through using a delta method approximation (see Appendix B). The (1 )100% Wald confidence interval for log(OR) is – The (1 )100% Wald confidence interval for OR is – Lui and Lin (Biometrical Journal, 2003, p. 231) show this interval is conservative. What does mean “conservative” here? Problems with small cell counts What happens to if a cell count is 0? When there is a 0 or small cell count, the estimator is changed a little to prevent problems. The estimator becomes Thus, 0.5 is added to each cell count. The estimate of becomes
= . This is derived through using a delta method approximation (see Appendix B). The (1 – )100% Wald confidence interval for log(OR) is The (1 – )100% Wald confidence interval for OR is Lui and Lin (Biometrical Journal, 2003, p. 231) show this interval is conservative. What does “conservative” mean here? Problems with small cell counts What happens to if a cell count is 0? When there is a 0 or small cell count, the estimator is changed a little to prevent problems. The estimator becomes Thus, 0.5 is added to each cell count. The estimate of becomes