The following appeared in a memo from the director of a large group of hospitals.

"In a controlled laboratory study of liquid hand soaps, a concentrated solution of extra strength UltraClean hand soap produced a 40 percent greater reduction in harmful bacteria than did the liquid hand soaps currently used in our hospitals. During our recent test of regular-strength UltraClean with doctors, nurses, and visitors at our hospital in Worktown, the hospital reported significantly fewer cases of patient infection (a 20 percent reduction) than did any of the other hospitals in our group. The explanation for the 20 percent reduction in patient infections is the use of UltraClean soap."

Write a response in which you discuss one or more alternative explanations that could rival the proposed explanation and explain how your explanation(s) can plausibly account for the facts presented in the argument.