andrew/split — pull request #96 by thomasmaas (2012-11-22 11:23:12+00:00)
Title: Fix for #94

... z-score of 1.65, corresponding to the positive half of the normal curve.

We are not interested in negative z numbers. The null hypothesis is
that the control is not performing worse. We only have to be confident
it's better to disprove the null hypothese, which means we only care
about the positive tail of the normal distribution.