Question

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

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

$\frac{x-55}{9}=1.405.$

$x=55+9*1.405\approx 68 min.$