Answer to Question #261910 in Statistics and Probability for desiree

Question

1.     The time for a major exam to be completed is normally distributed with an average of 55 minutes and a standard deviation of 9 minutes. If 92% of the students completed the exam, when should the test be terminated?

 

Answer 1

$P(Z<z)=0.92\to z=1.405.$

$\frac{x-55}{9}=1.405\to x=1.405*9+55\approx 68.$

The test should be terminated after 68 minutes.