"God and Evolution" reported that "a study of nearly 4,000 people in North Carolina, for example, found that frequent church-goers had a 46 percent lower risk of dying in a six-year period than those who attended less often. Another study involving nearly 126,000 participants suggested that a 20-year-old church-goer might live seven years longer than a similar person who does not attend religious services."13
a. Which study considers the relationship between two categorical variables-the first or the second one mentioned?
b. Tell what types of variables are involved in the other study, identifying each as being explanatory or response.