Using se (see Exercise 14.18) instead of  , rewrite
(a) The expression for t in Theorem 14.4;
(b) The confidence interval formula of Theorem 14.5.
Exercise 14.18
Show that
(a) ∑2, the random variable corresponding to 2, is not an unbiased estimator of σ2;
(b) S2e = n·∑2 / n–2 is an unbiased estimator of σ2. The quantity se is often referred to as the standard error of estimate.