This is a modification of Exercise 1. Suppose listeners to a late-night radio talk show were asked to call and report whether or not they had ever seen a ghost.
a. What is this type of sample called?
b. Do you think the proportion reporting that they had seen a ghost for the radio poll would be higher or lower than the proportion for a poll done using a random sample of adults in the United States? Explain.
Exercise 1
Refer to Exercise 2. The Roper Organization selected a random sample of adults in the United States for this poll. Suppose listeners to a late-night radio talk show were asked to call and report whether or not they had ever seen a ghost.
a. What is this type of sample called?
b. Do you think the proportion reporting that they had seen a ghost for the radio poll would be higher or lower than the proportion for the Roper poll? Explain.
Exercise 2
The Roper Organization conducted a poll in 1992 (Roper, 1992) in which one of the questions asked was whether or not the respondent had ever seen a ghost. Of the 1525 people in the 18- to 29-year-old age group, 212 said "yes."
a. What is the approximate margin of error that accompanies this result?
b. What is the interval that is 95% certain to contain the actual proportion of people in this age group who have seen a ghost?