A study by the Institute for Fiscal Studies (Goodman & Greaves, 2010) found that parents’ marital status when a child was born predicted the likelihood of the relationship’s demise. Parents who were cohabitating when their child was born had a 27% chance of breaking up by the time the child was 5, whereas those who were married when their child was born had a 9% chance of breaking up by the time the child was 5—a difference of 18%. The researchers, however, reported that cohabiting parents tended to be younger, less affluent, less likely to own a home, less educated, and more likely to have an unplanned pregnancy. When the researchers statistically controlled for these variables, they found that there was just a 2% difference between cohabitating and married parents. 

a. What are the independent and dependent variables used in this study? 

b. Were the researchers likely to have used simple linear regression or multiple regression for their analyses? Explain your answer. 

c. In your own words, explain why the ability of marital status at the time of a child’s birth to predict divorce within 5 years almost disappeared when other variables were considered. Explain your answer. 

d. Name at least one additional “third variable” that might have been at play in this situation. Explain your answer.