The owners of a large shopping complex wondered if there was a relationship between how customers traveled to the complex and whether or not they made a purchase. They observed a random sample of 100 customers and categorized each of them based on transportation method and whether or not they made a purchase.
What type of statical test used in this case?

A. A z-test for a proportion
B. A χ2 goodness of fit test
C. A χ2 test for homogeneity
D. A χ2 test of independence
E. A two-sample z-test for a proportion