What is the difference of a control variable and a constant in an experiment?

here is the problem


The first group was not promised any candy if they did well on the quiz. The second group was promised 1 candy bar if they did well on the quiz. The third group was promised 2 candy bars if they did well on the quiz. The forth group was promised 3 candy bars if they did well on the quiz.





Group #1 got an average of 70% on the quiz.


Group #2 got an average of 80% on the quiz.


Group #3 got an average of 90% on the quiz.


Group #4 got an average of 95% on the quiz





give 2 control variables and 1 constantWhat is the difference of a control variable and a constant in an experiment?
The variables are 1) the people taking the quiz 2) the amount of candy each group is promised. The constant is the quiz itself. Variables change, constants stay the same.What is the difference of a control variable and a constant in an experiment?
The candy bar is assumed to be a constant quantity of reward (or candy) per bar in this experiment, since no information is given about its size. Only its count is a variable quantity.





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Regards,





John Popelish