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Chapter 11: Q. 11.35 (page 460)
Obtain a sample size that will ensure a margin of error of at most the one specified.
Margin of error
Confidence level
The required sample size is
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In a New York Times article "More Mother Breast-Feed, in First Months at Least," G. Harris reported that new mothers breast-feed their infants at least briefly, the highest rate seen in the United States in more than a decade. His report was based on data for infants from the National Health and Nutrition Examination Survey, which involved in-person interviews and physical examinations. Find a confidence interval for the percentage of all new mothers who breast-feed their infants at least briefly.
confidence interval
Folic Acid and Birth Defects. For several years, evidence had been mounting that folic acid reduces major birth defects. A. Creizel and I. Dudas of the National Institute of Hygiene in Budapest directed a study that provided the strongest evidence to date. Their results were published in the paper "Prevention of the First Occurrence of Neural-Tube Defects by Periconceptional Vitamin Supplementation" (New England Journal of Medicine, Vol. 327(26). p. 1832 ). For the study, the doctors enrolled women prior to conception and divided them randomly into two groups. One group, consisting of 2701 women, took daily multivitamins containing mg of folic acid; the other group, consisting of 2052 women, received nay A. Creizel and L. Duxlas of the National Institute of Hygiene i) Budapest directed a study that provided the strongest evidence to date Their results were published in the paper "Prevention of the Firs Occurrence of Neural-Tube Defects by Periconceptional Vitamin Supplementation" (New England Journal of Medicine, Vol. 327(26). p. 1832 ). For the study, the doctors enrolled women prior to conception and divided them randomly into two groups. One group, consisting of 2701 women, took daily multivitamins containing mg of folic acid; the other group. consisting of 2052 women, received only trace elements. Major birth defects occurred in 35 cases when the women took folic acid and in 47 cases when the women did not.
a. At the significance level, do the data provide sufficient evidence to conclude that women who take folic acid are at lesser risk of having children with major birth defects?
b. Is this study a designed experiment or an observational study? Explain your answer.
c. In view of your answers to parts (a) and (b), could you reasonably conclude that taking folic acid causes a reduction in major birth defects? Explain your answer.
Margin of error
Confidence level
Educated guess
(a) Obtain a sample size that will ensure a margin of error of at most the one specified (provided of course that the observed value of the sample proportion is further from that of the educated guess.
(b). Compare your answer to the corresponding one and explain the reason for the difference, if any.
Vasectomies and Prostate Cancer. Refer to Exercise 11.106 and determine and interpret a confidence interval for the difference between the prostate cancer rates of men who have had a vasectomy and those who have not.
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