Answer:
Andy's proposal is more likely than Brad's to suffer from bias due to issues with "representativeness."
The above statement is True.
Step-by-step explanation:
AB testing compares the click-through rate of the two agencies only. This test runs on random basis. It is a straightforward exercise that affects the business in the short-run and its effect are temporary. While difference-in-difference testing studies the non-randomized data. The rates are higher but it covers the whole data.
Andy's proposal is more likely than Brad's to suffer from bias to issues with 'representatives'. Andy opts for A/B testing while Brad opts for difference-in-difference testing. Therefore, Andy's proposal is more likely to bias due to limited verification.
Hence, the given statement is
'True'