Planning and analysis of cross-over trials in infertility.

The use of cross-over trials in investigating treatments for infertility is discussed. A simple possible approach to analyzing such trials using the Mantel-Haenszel procedure is explained. A more flexible approach based on the normal-binomial mixture model of Ezzet and Whitehead is examined. It is shown how this may be implemented in various statistical packages by applying it to two real examples of trials in infertility. An approach that may be used to compare designs via simulation is explained briefly. It is concluded that provided that cross-over trials in infertility are regarded as parallel group trials with extra information rather than as cross-over trials with missing information, their use may be more promising than that has previously been concluded.