Date X cleanser Y cleanser none
5/18/11 0 0 0
5/19/11 0 0.25 0.50
5/20/11 0 1.0 1.25
5/21/11 0.20 2.75 3.0
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Which of the following is a constant, or control variable, in this experiment?
The brand of cleanser that didn't work. (MY ANSWER)
The results observed over four days.
The brand of cleanser that worked best.
To determine which variable is the constant or control variable in this experiment, let's first understand the purpose of a control variable. A control variable is a factor that is kept constant or unchanged throughout an experiment. Its purpose is to provide a baseline comparison against which the effects of other variables can be measured.
In this given experiment, we have two brands of cleansers being tested (X cleanser and Y cleanser) and also a condition where no cleanser is used (none). The results observed over the four days are not constant, as we see changes in the amount of cleanser used and the effectiveness of the cleansers.
The brand of cleanser that didn't work is also not constant because it is part of the variables being tested. We see that on some days, both cleansers are ineffective, while on other days, one might be more effective than the other.
Therefore, the constant, or control variable, in this experiment would be the brand of cleanser that worked best. This brand remains constant throughout the experiment and serves as a point of comparison to evaluate the effectiveness of the other cleansers.