On the validity of Fisher's z test when applied to an actual example of non-normal data. (With five text-figures.)

1. Previous work on the validity of the t and z tests on non-normal distributions is described. The question as to whether these tests, which are all on small samples from theoretical distributions, are really apposite is discussed.2. The necessity of making a practical test with actual data which shall comply with the usual conditions obtaining in agricultural experiments is urged.3. A practical test has been made on a skew distribution obtained from the observation of 256 height measurements on wheat. The distribution of the values of R. A. Fisher's z from a thousand random samples has been obtained and found to agree satisfactorily with the theoretical distribution.