Question

84 students who took the achievement test last Oct. 2020 If the mean is 88, s = 2.50. how many students scored above the mean?

Answer 1

$P(X>88) = 1-P(X<88) \\ = 1 -P(Z< \frac{88-88}{2.5}) \\ = 1 - P(Z<0) \\ = 1 -0.5 \\ = 0.5 \\ n=84 \\ Expected = np = 84 \times 0.5 = 42$