Consider the following. (Enter your answers to four decimal places.)
(a) Find the level of confidence assigned to an interval estimate of the mean formed using the interval x - 1.04 · ?x to x + 1.04 · ?x.
(b) Find the level of confidence assigned to an interval estimate of the mean formed using the interval x - 1.59 · ?x to x + 1.59 · ?x.
(c) Find the level of confidence assigned to an interval estimate of the mean formed using the interval x - 1.84 · ?x to x + 1.84 · ?x.
(d) Find the level of confidence assigned to an interval estimate of the mean formed using the interval x - 2.07 · ?x to x + 2.07 · ?x.