Clojure for Data Science

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 ...