90%; n = 200; = 15.0; population appears to be skewed. Assume that we want to

90%; n = 200; σ = 15.0; population appears to be skewed.

Assume that we want to construct a confidence interval using the given confidence level. Do one of the following, as appropriate: (a) Find the critical value z_α/2, (b) find the critical value t_α/2, (c) state that neither the normal nor the t distribution applies.