Question

how do i do problems like this? " the time required to finish a test is normally distributed with a mean of 60 minutes and a standard deviation of 10 minutes. what is the probability a student will finish the test between 50 and 60 minutes?"

Answer 1

Let the time taken to finish the test be x.
P(50 < x < 60) = P(x < 60) - P(x < 50) = P(z < (60 - 60)/10) - P(z < (50 - 60)/10) = P(z < 0) - P(z < -1) = P(z < 0) - (1 - P(z < 1)) = P(z < 0) + P(z < 1) - 1 = 0.5 + 0.8413 - 1 = 0.3413