Suggest the following. (Enter your answers to four decimal places.)
(a) Determine the level of confidence assigned to an interval estimate of the mean formed using the interval x - 1.16 · ?x to x + 1.16 · ?x.
(b) Determine the level of confidence assigned to an interval estimate of the mean formed using the interval x - 1.44 · ?x to x + 1.44 · ?x.
(c) Determine the level of confidence assigned to an interval estimate of the mean formed using the interval x - 1.74 · ?x to x + 1.74 · ?x.
(d) Determine the level of confidence assigned to an interval estimate of the mean formed using the interval x - 2.06 · ?x to x + 2.06 · ?x.