Are young couples who marry or cohabitate more likely to gain weight than those who stay single? Researchers followed 8000 men and women for 7 years. At the start of the study, none of the participants were married or living with a romantic partner. The researchers found that women who married or cohabitated during the study gained 9 pounds more than single women, and married or cohabitating men gained, on average, 6 pounds more than single men.
(a) Why is this an observational study? What type of observational study is this?
(b) What is the response variable in the study? What is the explanatory variable?
(c) Identify some potential lurking variables in this study.
(d) Can we conclude that getting married or cohabiting causes one to gain weight? Explain.