10.5 Risky behaviors among HIV positive female sex workers In 2014, questionnaire surveys were administrated among 181 female sex workers in the Yunnan province of China who confirmed themselves to be HIV positive (www.ncbi.nlm.

gov/pubmed/26833008). The participants were divided into two age groups—76 cases were below 35 years and 105 cases were 35 years old and above. 26 females below 35 years and 54 females of ages 35 years and above reported using drugs.

Let p1 and p2 denote the population proportions of females below 35 years and of females 35 years or above who took drugs, respectively.

a. Report point estimates of p1 and p2.

b. Construct a 95% confidence interval for 1p1 - p22, specifying the assumptions you made to use this method. Interpret.

c. Based on the interval in part

b, explain why the proportion using drugs may have been quite a bit larger for females of ages 35 years or above, or it might have been only moderately larger.