Question

A scientist is testing the effectiveness of Drug X on cancer. She gives a small amount of the drug to mice that have cancer. She gives each mouse a different amount from 1 to 10 grams, and then measures the size of the tumor in each mouse before the drugs and two weeks after the drugs. She gives one of the mice sugar instead of Drug X. What is her independent variable in this experiment?

Answer 1

Two weeks after: the tumor may decrease if the drug is appropriate
It tests the placebo effect in mice by giving them sugar, the tumor should be the same size.

Answer 2

Answer:

The amount of drug X is an independent variable

Explanation:

An independent variable is the one which is not affected by any factor in an experiment and remains constant. Here in this experiment the amount of drug  given to mice is an independent variable. The quantity of drug given to mice remains fixed till the end of the experiment. While the size of tumor and effect of drug on mice varies with the amount of drug given thus these two are dependent variable.

Hence, the amount of drug X is an independent variable.