Comment on J. Berkson's paper “in dispraise of the exact test”

This paper rejects the preference expressed by Berkson for the heuristic test statistic T_N with standard normal distribution testing equality of two binomial probabilities in favour of Fisher's conditional exact test statistic T_E. Conditioning upon k₁ + k₂ = k shows that T_N admits too large first kind error probabilities. But also unconditionally T_N is systematically too large compared to T_E, giving too small critical levels at given experimental outcomes and power which is misleadingly too large. This is mainly due to the fact that T_N is not suitably corrected for continuity (at small sample sizes).