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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
To assess the accuracy of a laboratory scale, a standard weight known to weigh grams is weighed repeatedly. The scale readings are Normally distributed with unknown mean (this mean is grams if the scale has no bias). In previous studies, the standard deviation of the scale readings has been about gram. How many measurements must be averaged to get a margin of error of with confidence? Show your work.
Hallux abducto valgus (call it HAV) is a deformation of the big toe that is fairly uncommon in youth and often requires surgery. Doctors used -rays to measure the angle (in degrees) of deformity in a random sample of patients under the age of who came to a medical center for surgery to correct HAV. The angle is a measure of the seriousness of the deformity. For these patients, the mean HAV angle was degrees and the standard deviation was degrees. A dot plot of the data revealed no outliers or strong skewness.
(a) Construct and interpret a confidence interval for the mean HAV angle in the population of all such patients.
(b) Researchers omitted one patient with an HAV angle of degrees from the analysis due to a measurement issue. What effect would including this outlier have on the confidence interval in (a)? Justify your answer.
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 鈥� boys) is to . Interpret the confidence interval and the confidence level.
Interpret your interval in context.
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