Stats

#1
The length of time for students to complete the Statistics final exam is normally distributed with mean 75 minutes and standard deviation 15 minutes. How much time should be allowed so that 90% of the students will finish the exam?

We use .4000 instead of .9000
.4000= .3997
=1.28

x=u = zo
=75 + 1.28(2)
=75 + 2.56
=77.56

78minutes

Is this right?