Unconditional confidence intervals (CIs) for the difference between marginal proportions in matched pairs data have essentially been based on improvements of Wald’s large-sample statistic. The latter are approximate and non-conservative. In some situations it may be of importance that CIs are conservative, e.g. when claiming bio-equivalence in small samples. Existing methods for constructing conservative CIs are computer intensive and are not suitable for sample size determination in planned studies. This paper presents a new simple method by which conservative CIs are readily computed. The method gives CIs that are comparable with earlier conservative methods concerning coverage probabilities and lengths. However, the new method can only be used if the proportions in the discordant cells p and q satisfies , but this is luckily the case in most applications and several examples are given. The new method is compared with previously suggested approximate and exact methods in large-scale simulations.
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