Gender in two-child families. Refer to the Human Biology

(Feb. 2009) study on the gender of children in two-child families, Exercise 4.29 (p. 222). The article reported on the results of the National Health Interview Survey (NHIS) of 42,888 two-child families. The table below gives the number of families with each gender configuration.

Gender Configuration Number of Families Girl-girl (GG) 9,523 Boy-girl (BG) 11,118 Girl-boy (GB) 10,913 Boy-boy (BB) 11,334

a. If it is just as likely to have a boy as a girl, find the probability of each of the gender configurations for a two-child family.

b. Use the probabilities, part

a, to determine the expected number of families for each gender configuration.

c. Compute the chi-square test statistic for testing the hypothesis that it is just as likely to have a boy as a girl.

d. Interpret the result, part

c, if you conduct the test using a = .10.

e. Recent research indicates that the ratio of boys to girls in the world population is not 1 to 1, but instead higher (e.g., 1.06 to 1). Using a ratio of 1.06 to 1, the researchers showed that the probabilities of the different gender configurations are: GG—.23795, BG—.24985, GB—.24985, and BB—.26235. Repeat parts b–d using these probabilities.