Aclothing manufacturer is curious if celebrity endorsements will influence a customer's decision
in buying its products. this clothing manufacturer premieres its latest series of commercials
privately to two separate groups of potential shoppers. one group will see a series of
commercials without celebrities, and one group will see a series of commercials with celebrities.
furthermore, the manufacturer decides to split up the male shoppers from the female shoppers.
grouping the shoppers together by gender is an example of what?
a) reduction of confounding factors
b) matching
c) factoring
d) blocking
e) stratifying