A recent newspaper article reported the results of a survey

A recent newspaper article reported the results of a survey of well-educated suburban parents. The responses to one question indicated that by age 2, children were watching an average

Solution

P(X>90) = P((X-mean)/s >(90-60)/20) = P(Z>1.5) =0.0668 (from standard normal table)

P(X<20) = P(Z<(20-60)/20) = P(Z<-2) =0.0228 (from standard normal table)