The area between the main content page and the page edges

Margin!

Explanation:

In typography, a margin is the area between the main content of a page and the page edges. The margin helps to define where a line of text begins and ends.

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Independent

Explanation:

An experiment can be defined as an investigation which typically involves the process of manipulating an independent variable (the cause) in order to be able to determine or measure the dependent variable (the effect).

This ultimately implies that, an experiment can be used by scientists to show or demonstrate how a condition causes or gives rise to another i.e cause and effect, influence, behavior, etc in a sample.

In an experiment , the variable being manipulated by an experimenter is known as an independent variable while the dependent variable is the event expected to change when the independent variable is manipulated.

Hence, independent variable describes the variable that is changed to test the prediction.