6. alex wanted to find out what toothpaste made teeth the cleanest. everyday she brushed her
teeth with a different product and then took a plaque test to see how much plaque was left.
she used crest, colgate, close-up, and water.
a. independent variable (iv): tume of toothpaste
b. dependent variable (dv): how much piaque (as loft
c. control:
d. constants:

a) Independent variable (IV): toothpase brand

b) Dependent variable (DV): amount of plaque left

c) Control: water

d) Constants: amount of toothpaste, kind of toothbrush, how long the toothbrushing took.

Explanation:

In an experiment there usually be independent variable, dependent variable, control gropus, and constants.

The independendent variable is the variable whose impacts on other varbiale. Then, the independent variable is manipulated or changed by the scientist (the person that designs or perform the experiment).

In this case, Alex is changing the brand of toothpaste: Crest, Colgate, and Close-Up. So the answer to the first question is brand of toothpaste:

The dependent variable is the variable that changes by the effect of changing the independent variable. It is the variable whose behavior you want to explain in terms of the independent variable.

In this case, Alex wants to determine the effect of the toothtpaste brand on the plaque, so the dependent variable is how much plaque is  left.

The control is a group of experiments used for comparison. This is, you do not include the independent variable in them. In this example it is the set of experiments made with only water. The scientist will be able to compare the results of using toothpase with no using toothpaste on the plaque when he includes a group of experiments where no toothpaste is used but water.

In order to state if it is the change in the independent variable what causes or explains the results on the dependent variable, the scientist must make sure that no other changes occur during the experimentation.

In this case, it is not stated which other conditions Alex made sure to remain constant, but for sure they should include the amount of toothpaste used, the kind of teethbrush, and the time of brushing.