Global Pharmaceutical Research and Development, Statistics, Abbott Laboratories, Building AP9A-1, 100 Abbott Park Road, Abbott Park, IL 60064, USA. yu.shu@abbott.com
When hypotheses concerning the sensitivity and specificity of a binary medical diagnostic test are simultaneously tested using a group sequential procedure, constructing point and interval estimates of the parameters is challenging because there is no unique way to order sample points in the two-dimensional space. In this paper, upon termination of a group sequential procedure, we compare the bias and mean squared errors of the maximum-likelihood and Rao-Blackwell unbiased estimators of sensitivity and specificity. Confidence intervals (CIs) of the two parameters were constructed using normal approximation and Woodroofe's pivot methods based on maximum-likelihood and Rao-Blackwell unbiased estimates. The coverage probability and the expected length of CIs for the parameters were compared by simulation studies.