Answer to Question #199796 in Statistics and Probability for Ester Nekundi

Question

Test marks (%) obtained in a test are normally distributed with a mean of 55 % and variance of 400 (% squared).

what is the probability that a randomly selected student scored below 40%?

Answer 1

$P(X<40)=P(Z<\frac{40-55}{20})=P(Z<-0.75)=0.2266.$