Question

A simple random sample has a sample size of n = 65. Given the population is normally distributed, find the critical value ta/2 corresponding to a 99% confidence level.

a) 2.678

b) 2.575

c) 2.000

d) 2.660

Answer 1

Given that, sample size (n) = 65

=> Degrees of freedom = 65 - 1 = 64

Therefore, using t-table, we get, t-critical value at significance level of 0.01 with 64 (in table see df = 60) is ta/2 = 2.660

Answer : d) 2.660

Note : if we used standard normal z-table, then critical value = 2.575