Chapter 8: Q 37. (page 522)
More online sales Refer to Exercise 35. Calculate and interpret the standard error of for these data.
Short Answer
The value of standard error is.
Chapter 8: Q 37. (page 522)
More online sales Refer to Exercise 35. Calculate and interpret the standard error of for these data.
The value of standard error is.
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Get started for freeBone loss by nursing mothers Breast-feeding mothers secrete calcium into
their milk. Some of the calcium may come from their bones, so mothers may lose bone mineral. Researchers measured the percent change in bone mineral content (BMC) of the spines of randomly selected mothers during three months of breast-feeding. The mean change in BMC was and the standard deviation was
a. Construct and interpret a confidence interval to estimate the mean percent change in BMC in the population of breast-feeding mothers.
b. Based on your interval from part (a), do these data give convincing evidence thatnursing mothers lose bone mineral, on average? Explain your answer.
A quality control inspector will measure the salt content (in milligrams) in a random
sample of bags of potato chips from an hour of production. Which of the following would result in the smallest margin of error in estimating the mean salt content ?
a. confidence;
b. confidence;
c. confidence;
d. confidence;
e. n = 100 at any confidence level
Employment in CaliforniaEach month the government releases unemployment
statistics. The stated unemployment rate doesn’t include people who choose not to be employed, such as retirees. Based on a random sample of California adults, a confidence interval for the proportion of all California adults employed in the workforce is
a. Interpret the confidence level.
b. Name two things you could do to reduce the margin of error. What drawbacks do these actions have?
c. Describe how untruthful answers might lead to bias in this survey. Does the stated margin of error account for this possible bias?
Prayer in school A New York Times/CBS News Poll asked a random sample of U.S. adults the question “Do you favor an amendment to the Constitution that would permit organized prayer in public schools?” Based on this poll, the confidence interval for the population proportion who favor such an amendment is .
a. Interpret the confidence interval.
b. What is the point estimate that was used to create the interval? What is the margin of error?
c. Based on this poll, a reporter claims that more than two-thirds of U.S. adults favor such an amendment. Use the confidence interval to evaluate this claim.
Can you taste PTC? PTC is a substance that has a strong bitter taste for some people and is tasteless for others. The ability to taste PTC is inherited. About of Italians can taste PTC, for example. You want to estimate the proportion of Americans who have at least one Italian grandparent and who can taste PTC.
a. How large a sample must you test to estimate the proportion of PTC tasters within with confidence? Answer this question using the estimate 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?
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