Answer: A.Kelvin’s because he surveyed people leaving an area where food is sold
Step-by-step explanation:
Given: Kelvin and Lewie each design surveys in order to determine the number of people who buy food at the mall.
Kelvin surveys every other person leaving the food area.
Thus, he doesn't know about the people who do not buy food at mall whereas Lewie surveys every fifth person leaving the mall’s main entrance.
Thus, by this systematic random sampling he knows out of how many people the number of people buy food at mall.
Hence, Kelvin’s survey is likely to produce less valid results because he surveyed people leaving an area where food is sold.