Question

In a survey on supernatural experiences, 728 of 4009 adult Americans surveyed reported that they had seen or been with a ghost.

(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 adult Americans who have seen or been with a ghost?

1. We need to assume that there are only 728 adult Americans.

2. We need to assume that the 728 people are the only Americans who had seen or been with a ghost.    

3. We need to assume that the 4009 people were surveyed at a supernatural convention.

4. We need to assume that the 4009 people formed a random sample of adult Americans.

(b) Construct a 90% confidence interval for the proportion of all adult Americans who have seen or been with a ghost. (Round your answers to three decimal places.)

Interpret the interval.

1. We are 90% confident that the proportion of all adult Americans who have seen or been with a ghost is within this interval.

2. We are 90% confident that the proportion who have seen or been with a ghost is within this interval.    

3. We are confident that the proportion of all adult Americans who have seen or been with a ghost is within this interval 90% of the time.

4. We are confident that 90% of the proportion of all adult Americans who have seen or been with a ghost is within this interval.

(c) Would a 99% confidence interval be narrower or wider than the interval computed in part (b)?

1. narrower

2. wider    

Answer 1