title: A new procedure for the statistical evaluation of intrauterine contraception.
abstract: An improved statistical method for assessing the efficacy of intrauterine contraception is presented. This method, called the log-rank method, is based on a daily life table, which yields the best estimates of the cumulative net termination probabilities. It provides a sensitive chi-square test statistic to detect differences among these probabilities for two or more contraceptive devices. When three or more devices are compared, the chi-square statistic may be partitioned into additive components representing comparisons among groups of devices. The log-rank method also permits adjusting for differences among subgroups by controlling for factors such as parity or age. Although calculations may be performed on a desk calculator, a FORTRAN-IV computer program is made available to interested researchers.
mesh_terms: D003201:Computers; D003267:Contraception / Q000379:methods*; D003273:Contraceptive Devices; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D007434:Intrauterine Devices; D011247:Pregnancy; D013223:Statistics as Topic