Assignment 7

8.58

8.71

9.37

9.41

9.50

8.58 Teeth and military service.

In 1898 the United States and Spain fought a war over the U.S. intervention in the Cuban War of

Independence. At that time the U.S. military was concerned about the nutrition of its recruits. Many did not have a sufficient number of teeth to chew the food provided to soldiers. As a result, it was likely that they would be undernourished and unable to fulfill their duties as soldiers. The requirements at that time specified that a recruit must have "at least four sound double teeth, one above and one below on each side of the mouth, and so opposed" so that they could chew food. Of the 58,952 recruits who were under the age of 20,68 were rejected for this reason. For the 43,786 recruits who were 40 or over, 3801 were rejected.

(a) Find the proportion of rejects for each age group.

(b) Find a 99% confidence interval for the difference in the proportions.

(c) Use a significance test to compare the proportions. Write, a short paragraph describing your results and conclusions.

(d) Are the guidelines for the use of the large-sample approach satisfied for your work in part (b) and (c)? Explain your answers.

8.71 Gender bias in textbooks.

To what extent do syntax textbooks, which analyze the structure of sentences, illustrate gender bias? A study of this question sampled sentences from 10 texts.23 One part of the study examined the use of the words "girl," "boy," "man," and "woman." We will call the first two wordsjuvenileand the last two adult. Is the proportion of female references that are juvenile (girl) equal to the proportion of male references that are juvenile (boy)? Here are data from one of the texts:

\fGender n X (juvenile) Female 60 48 Male 132 52