Performing the t-test
The difference in the way t-test works stems from the probability distribution from which our p-value is calculated. Having calculated our t-statistic, we need to look up the value in the t-distribution parameterized by the degrees of freedom of our data:
(defn t-test [a b] (let [df (+ (count a) (count b) -2)] (- 1 (s/cdf-t (i/abs (t-stat a b)) :df df))))
The degrees of freedom are two less than the sizes of the samples combined, which is 298 for our samples.
Recall that we are performing a hypothesis test. So, let's state our null and alternate hypotheses:
- H0: This sample is drawn from a population with a supplied mean
- H1: This ...