Students in Ms. Winters' class were interested in testing the antibacterial strength of hand soap versus hand sanitizer. The students planned to wash their hands using the sanitizer or soap and warm water for two minutes, then dry their hands with a paper towel. The standard of comparison would be rubbing their hands vigorously for 2 minutes in warm water, without any soap or sanitizer, and then drying with a paper towel. The sanitizer advertisement claimed to kill bacteria more effectively than any soap. After washing, hands would be swabbed and then the swab applied to a culture plate and incubated. Finally, the bacterial cultures would be counted. What would be an appropriate research question to guide this scientific investigation