Question

The time required to finish a test normally distributed with a mean of 60 minutes and a standard deviation of 10 minutes. What is the probability that a student will finish the test between 40 and 70 minutes?

Answer 1

P(40<X<70) = P[(40-60)/10 < z < (70-60)/10] = P(-2 < z < 1)

Next re-write so that it can be looked up in a Standard Normal table

P(-2 < z < 1) = P(z < 1) - P(z < -2) = 0.8413 - 0.0228 = 0.8185

Answer 2

is .8185 the answer?

Answer 3

Yes

Answer 4

does that need to have a percentage answer? Should it be in percentage form?

Answer 5

No just like that