What percentage of the population scored over 80 points on this exam

Question

Standard deviation (16)

Mean score (100)

Answer 1

x = score, want to compute P(x > 80)

z = (x - mean) / SD

compute z for x = 80, mean = 100, SD = 16

z = (80 - 100) / 16 = -1.25

P(x > 80) = P(z > -1,25) = 1 - P(z < -1.25) = 1 - 0.1056 = 0.8944