A hand sanitizer was advertised to be more effective at killing bacteria than any antibacterial soap. Students were split evenly into 4 groups to test this claim. Groups 1-3 washed their hands using the assigned hand sanitizer or soap (see table) and warm water for two minutes, and then dried their hands with a paper towel. Group 4 rubbed their hands vigorously for 2 minutes in warm water, without any soap or sanitizer, and then dried their hands with a paper towel. After washing, each student’s hands were swabbed and the swab was applied to a culture plate and incubated. Finally, the bacterial cultures were counted. what is the independent variable?

Group 4

Explanation:

The control group in this case would be those students in group 4.

The control group during an experiment is a group that does not receive the treatment administered to other groups and as such used as a standard for measuring the effects of the treatment on other groups. Whatever differences that exist between the control group and the various treatment groups is attributed to be as a result of the treatment administered to the groups.

In this case, group 4 only used warm water for washing their hands instead of the hand sanitizer/soap used by the other groups. Whatever differences found out in the bacterial count in their respective culture swabs can be attributed to the effects of the hand sanitizer/soap.

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