Question

1. we want to see if a mouses diet affects how quickly they can do a maze.

a. independent variable:
b. dependent variable:

1. we want to see if energy bars help students run for longer periods of time.

a. independent variable:
b. dependent variable:

1. we want to see if special dog foods help dogs lose weight.

a. independent variable:
b. dependent variable:

Explanation:

In an experiment, the independent variable is what is changed or manipulated, and the dependent variable is what is measured and affected by the independent variable.
For question 7: The diet is manipulated to see its effect on maze - completion time. For question 8: The presence or absence of energy bars is manipulated to see its effect on running time. For question 9: The type of dog food is manipulated to see its effect on weight loss.

Answer:

7.
a. Mouse's diet
b. How quickly the mouse can do a maze
8.
a. Energy bars (presence or absence)
b. How long students can run
9.
a. Special dog foods
b. Dogs' weight loss