from Problems the text
-----------------------
Section 6-3
10: Find the confidence interval assuming a normal population:
Salaries of Airline pilots: 99% confidence, n = 12, xbar = $97,334,
s = $17,747.
14: If we refer to the weights (in grams) of quarters listed in Data Set
13 in Appendix B, we will find 50 weights with a mean of 5.622 grams and a
standard deviation of 0.068 grams. Based on this random sample of quarters
in circulation, construct a 98% confidence interval estimate of the population
mean weight of all quarters in circulation. The U.S. Department of the
Treasury claims that it mints quarters to yield a mean weight of 5.670g.
Is this claim consistent with the confidence interval? If not, what is a
possible explanation for the discrepency?
Section 6-4
2. The Franklin Vending Machine company must adjust its machines to accept only
coins with specified We weights. will obtain a sample of quarters and weigh
them to determine the mean. How many quarters must we randomly select and
weigh if we must be 99% confident that the sample mean is within 0.025g of
the true population mean of all quarters? If we use the sample of quarters
in Data set 13 in Appendix B, we can estimate that the populations
standard deviation is 0.068g.
8. You have just been hired by the Boston Marketing Company to conduct a
survey to estimate the mean amount of money spent by movie patrons (per
movie) in Massachusetts. First use the range rule of thumb to make a rough
estimate of the standard deviation of the amounts spent. It is reasonable to
assume that typical amounts range from $3 to about $15. Then use the
estimated standard deviation to determine the sample size corresponding
to 98% confidence and a 25 cent margin of error.