## Function D-Test

(

**d-test** &rest < args > )

d-test (sample-1 sample-2 tails &key (times 1000) (h0mean 0))

Two-sample test for difference in means. Competes with the unmatched,

two-sample t-test. Each sample should be a sequence of numbers. We calculate

the mean of ` sample-1' minus the mean of `

sample-2'; call that D. Under the null

hypothesis, D is zero. There are three possible alternative hypotheses: D is

positive, D is negative, and D is either, and they are selected by the `tails'

parameter, which must be :positive, :negative, or :both, respectively. We count

the number of chance occurrences of D in the desired rejection region, and

return the estimated probability.