Chapter 6, Problem 19P

1. A report in 20 l0 indicates that Americans between the ages of 8 and 18 spend an average of µ=7.5 hours
per day using some sort of electronic device such as smart phones, computers, or tablets. Assume that: the distribution of times is normal with a standard deviation of $\sigma =2.5$hours and find the following values.

What is the probability of electing an individual who

uses electronic devices more than 12 hours a day?

What proportion of 8 to 18 year- old Americans

spend between 5 and l0 hours per day using electronic devices? In symbols, p(5 < X < 10) =?