Chapter 8: Q. 38 (page 496)
Teens" online profiles Describe a possible source of error that is not included in the margin of error for the confidence interval in Exercise 36
There are possible sources of errors.
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In each of the following situations, discuss whether it would be appropriate to construct a one-sample interval to estimate the population mean.
(a) We want to estimate the average age at which U.S. presidents have died. So we obtain a list of all U.S. presidents who have died and their ages at death.
(b) How much time do students spend on the Internet? We collect data from the members of our AP Statistics class and calculate the mean amount of time that each student spent on the Internet yesterday.
(c) Judy is interested in the reading level of a medical journal. She records the length of a random sample of words from a multipage article. The Minitab histogram below displays the data.
The AP Statistics class in Exercise also asked an SRS of boys at their school how many shoes they have. A confidence interval for the difference in the population means (girls โ boys) is to . Interpret the confidence interval and the confidence level.
School vouchers A national opinion poll found that % of all American adults agree that parents should be given vouchers that are good for education at any public or private school of their choice. The result was based on a small sample.
(a) How large an SRS is required to obtain a margin of error of (that is, ) in a % con๏ฌdence interval? Answer this question using the previous pollโs result as the guessed value for .
(b) Answer the question in part (a) again, but this time use the conservative guess . By how much do the two sample sizes differ?
1. In the companyโs prior-year survey, 80% of customers surveyed said they were โsatisfiedโ or โvery satisfied.โ Using this value as a guess for pห, find the sample size needed for a margin of error of 3% at a 95% confidence level.
What if the company president demands 99% confidence instead? Determine how this would affect your answer to Question 1.
98% Confidence find for aconfidence interval using table A or tour calculator. show your method.
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