do one of the following as appropriate: a) find the critical value z a/2, b) find the critical value t a/2, c) state that neither the normal nor the t-distribution applies. Confidence level is 95%. n=28. o is known. Population appears to be very skewed. A). Za/2 = 1.96 B). Za/2 = 1.645 C). ta/2 = 2.052 D). ta/2 = 1.703 E). Neither normal nor t distribution applies.