NOTE: If you just wanted the probability that the sample would contain 18 or fewer blacks, given that the mayor is correct, you would compute zc as shown in step d. Then, F(-2.53) = 1 - F(2.53) = .0057 (or, with correction for continuity, F(-2.42) = .0078). Hence, there is less than a 1% chance that the mayor could be correct and the sample only contain 18 or fewer supporters.