In a survey on supernatural experiences, 724 of 4003 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 724 adult Americans.We need to assume that the 4003 people were surveyed at a supernatural convention. We need to assume that the 4003 people formed a random sample of adult Americans.We need to assume that the 724 people are the only Americans who had seen or been with a ghost.
(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 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 the proportion of all adult Americans who have seen or been with a ghost is within this interval 90% of the time.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
a) The 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 the 4003 people formed a random sample of adult Americans.
b) Here
sample proportion
and sample size
a 90% confidence interval for the proportion of all adult Americans who have seen or been with a ghost
Interpretation : We are 90% confident that the proportion who have seen or been with a ghost is within this interval.
c) Since confidence coefficient of 99% confidence interval > confidence coefficient of 95% confidence interval,
so the interval would be wider.
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