In a survey on supernatural experiences, 716 of 4005 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?
We need to assume that there are only 716 adult Americans. We need to assume that the 4005 people formed a random sample of adult Americans. We need to assume that the 716 people are the only Americans who had seen or been with a ghost. We need to assume that the 4005 people were surveyed at a supernatural convention.
(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.
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. We are 90% confident that the proportion of all adult Americans who have seen or been with a ghost is within this interval. We are 90% confident that the proportion who have seen or been with a ghost is within this interval. 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)?
narrowerwider