The experimenter assigns the subjects to conditions, administers the treatments, and measures the outcome in such a way that there is only one relevant difference between the conditions being compared. this difference between the conditions is called the:

Independent variable

Explanation:

The experimenter assigns the subjects to conditions, administers the treatments, and measures the outcome in such a way that there is only one relevant difference between the conditions being compared. This difference between the conditions is called the independent variable. As independent variables are condition tested and they are controlled by the investigator; used in statistics to predict or explain a dependent variable.  It is not controlled by the participants.

conformal maps greatly distort _sizes_ of continents in higher latitudes.

the answer is sizes.