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Chapter 8: Q. 32 (page 496)
confidence Find confidence interval using Table A or your calculator. Show your method.
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Bone loss by nursing mothers.: Breastfeeding mothers secrete calcium into their milk. Some of the calcium may come from their bones, so mothers may lose bone minerals. Researchers measured the per cent change in bone mineral content (BMC) of the spines of randomly selected mothers during three months of breastfeeding. The mean change in BMC was and the standard deviation was .
(a) Construct and interpret a 99% confidence interval to estimate the mean per cent change in BMC in the population.
(b) Based on your interval from (a), do these data give good evidence that on average nursing mothers lose bone minerals? Explain
Gambling and the NCAA Gambling is an issue of great concern to those involved in college athletics. Because of this concern, the National Collegiate Athletic Association (NCAA) surveyed randomly selected student-athletes concerning their gambling-related behaviors.Of the Division I male athletes in the survey, reported participation in some gambling behavior. This includes playing cards, betting on games of skill, buying lottery tickets, betting on sports, and similar activities. A report of this study cited a % margin of error.
(a) The con铿乨ence level was not stated in the report. Use what you have learned to 铿乶d the con铿乨ence level, assuming that the NCAA took an SRS.
(b) The study was designed to protect the anonymity of the student-athletes who responded. As a result, it was not possible to calculate the number of students who were asked to respond but did not. How does this fact affect the way that you interpret the results?
Whelks and mussels The small round holes you often see in sea shells were drilled by other sea creatures, who ate the former dwellers of the shells. Whelks often drill into mussels, but this behavior appears to be more or less common in different locations. Researchers collected whelk eggs from the coast of Oregon, raised the whelks in the laboratory, then put each whelk in a container with some delicious mussels. Only whelks drilled into a mussel. The researchers want to estimate the proportion of Oregon whelks that will spontaneously drill into mussels.
It鈥檚 critical Find the appropriate critical value for constructing a confidence interval in each of the following settings.
(a) Estimating a population proportion p at a confidence level based on an SRS of size .
(b) Estimating a population mean M at a confidence level based on an SRS of size .
Teens and their TV setsAccording to a Gallup Poll report, % of teens aged to have TVs in their rooms. Here is part of the footnote to this report:
These results are based on telephone interviews with a randomly selected national sample of teenagers in the Gallup Poll Panel of households, aged to . For results based on this sample, one can say . . . that the maximum error attributable to sampling and other random effects is percentage points. In addition to sampling error, question-wording and practical dif铿乧ulties in conducting surveys can introduce error or bias into the 铿乶dings of public opinion polls.
(a) We omitted the con铿乨ence level from the footnote. Use what you have learned to determine the con铿乨ence level, assuming that Gallup took an SRS.
(b) Give an example of a 鈥減ractical dif铿乧ulty鈥� that could lead to biased results for this survey.
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