The report “Parents, Teens and Digital Monitoring” (Pew Research Center, January 7, 2016, pewinternet.org/2016/01/07/parents-teens-and-digital  -monitoring, retrieved April 4, 2018) reported that 61% of parents of teens age 13 to 17 said that they had checked which web sites their teens had visited. The 61% figure was based on a representative sample of 1060 parents of teens in this age group.

a. What assumption must be made in order for it to be appropriate to use the formula of this section to construct a confidence interval to estimate the proportion of all parents of teens age 13 to 17 who have checked which web sites their teens visit?

b. Construct and interpret a 90% confidence interval for the proportion of all parents of teens age 13 to 17 who have checked which web sites their teens visit.

c. Would a 99% confidence interval be narrower or wider than the interval calculated in Part (b)? Justify your answer.