A famous finding from social sciences is that couples who live together before they get married are more likely to get divorced. From this finding, many major news organizations have published stories suggesting that couples who want happy, healthy marriages that last should avoid moving in together before marriage. However, this finding was often calculated by comparing the average divorce rate of couples who lived together before marriage to the average divorce rate of couples who did not.
a. Give one reason why this comparison is affected by selection bias. To get full credit, you should explain how both living together before marriage and getting divorced are affected.
b. Describe a comparison that could be made which would not suffer from selection bias. It is okay if the comparison cannot be done in reality – I want to see if you understand how to eliminate selection bias.