Question

There are approximately one billion smartphone users in the world today. In the United States, the ages of smartphone users between 13 to 55 approximately follow a normal distribution with approximate mean and standard deviation of 37 years and 8 years, respectively.

Using the 68-95-99.7 Rule, what percent of smartphone users are between 29 and 53 years old? (Enter your answer as a percent to ONE decimal place. Do not include the % symbol.)

Answer 1

Solution :

Given that,

Using Empirical rule,

P( - 1< X < + 1) = 68%

P( - 2< X < + 2) = 95%

P( - 3< X < + 3) = 99.7%

P(29 < X < 53) = P(X < 53) - P(X < 29) = 0.975 - 0.16 = 0.815 = 81.5