Exact Power and Sample-Size Computations for the Cochran-Armitage Trend Test

The Cochran-Armitage test of trend is commonly used to determine if a dose-response relationship exists in a wide variety of biomedical settings including clinical trials, carcinogenicity studies, and toxicological risk assessment. For small, sparse, or unbalanced data sets, one generally adopts the exact version of the Cochran-Armitage test of trend for which numerical algorithms and software are readily available. No corresponding algorithms or software exist for the exact power and samplesize computations that are needed at design time, prior to gathering the data. This paper develops a network algorithm for computing the exact power of the Cochran-Armitage test of trend and applies it to several examples, thereby demonstrating that the corresponding asymptotic power computations can be rather misleading.