The article "Career Expert Provides DOs and DON'Ts for Job Seekers on Social Networking" (CareerBuilder.com, August 19, 2009) included data from a survey of 2667 hiring managers and human re- source professionals. The article noted that many employers are using social networks to screen job applicants and that this practice is becoming more common. Of the 2667 people who participated in the survey, 1200 indi- cated that they use social networking sites (such as Face- book, MySpace, and LinkedIn) to research job appli- seen or been with a ghost ("What Supernatural Experi- ences We've Had," USA Today, February 8, 2010).
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 pro- portion of all adult Americans who have seen or been with a ghost?
b. Construct and interpret a 90% confidence interval for the proportion of all adult Americans who have seen or been with a ghost.
c. Would a 99% confidence interval be narrower or wider than the interval computed in Part (b)? Justify your answer.