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 constant|||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.|||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