Just occasionally someone asks if everything we believe about causation-related science is wrong. This time, the use of the t-test is a cause of doubt. In the interpretation of rat lab results, animal experimenters use the t-test. The t-test, when used as originally designed, compares the means of two data distributions. The standard deviation of the distribution is first reduced to the standard error of the mean (SEM) and compared with the mean and SEM of the other distribution. If p < 0.05 it is pronounced that the two distributions are probably different. So, when comparing control animals with those dosed with a toxin the t-test is used to detect the likelihood that the toxin did anything. The reason for doubt is that SEM comparisons are only valid for true means. The single result e.g. 4 out of 90 rats developed lung cancer, is not a mean. Despite this, experimental scientists use the t-test to decide if 4/90 is different from 5/90. In fact the same experiment, when repeated, h