Answer:
The independent variable is how many maps/charts are made by a student.
Explanation:
The independent variable refers to the variable the researcher will manipulate while the dependent variable is the variable that is affected by the manipulation of the independent variable.
This means that the dependent variable outcome will depend on other variable which is the independent one.
In this example, you predict that exam scores are higher for students who created more maps/charts. In other means, the exam scores are being affected by the making of maps/charts to study (if you make more maps/charts, THEN you get a higher score). You can decide on how many maps/charts you will make but you cannot decide on what score you'll get on the exam, since you can manipulate the amount of maps/charts you will make, this is the independent variable.
Therefore, the independent variable is the making of maps/charts.
