Close Confidants and Social Networking Sites Exercise 6.116 on page 386 introduced a study in which 2006 randomly selected US adults (age 18 or older) were asked to give the number of people in the last six months ‘‘with whom you discussed matters that are important to you.” The average number of close confidants for the full sample is 2.2. In addition, the study asked participants whether or not they had a profile on a social networking site. For the 947 participants using a social networking site, the average number of close confidants is 2.5 with a standard deviation of 1.4, and for the other 1059 participants who do not use a social networking site, the average is 1.9 with a standard deviation of 1.3. (We examine a confidence interval involving these data in Exercise 6.237 on page 418.)

(a) What is the sample? What is the intended population?

(b) Is this an experiment or an observational study? Can we make causal conclusions from these data?

(c) Do the sample data provide evidence that those who use social networking sites tend to have more close confidants on average?

(d) Describe a possible confounding variable that might be influencing the association in part (c).

Exercise 6.116

34Hampton, K., Goulet, L., Rainie, L., and Purcell, K., ‘‘Social Networking Sites and Our Lives,” Pew Research Center, pewresearch. org, June 16, 2011.