The RoperASW Outlook survey was conducted via telephone among 1000 Americans ages 18 and older. The random sample is representative of the adult population in the United States. RoperASW reports that 73% of the people in the sample survey said that their biggest personal concern for the future was the rising cost of health care.
a. Show the 95% confidence interval estimate of the proportion of all adults in the population whose biggest personal concern is rising healthcare costs.
b. Identify the standard error and the margin of error terms in the interval.
c. Suppose RoperASW wants to reduce the margin of error in the 95% interval to .02 (2 percentage points). How much larger a sample would be needed? Treat the survey result reported above as a result from a pilot sample.