Answer:
a) Independent variable (IV): <u>toothpase brand</u>
b) Dependent variable (DV): <u>amount of plaque left</u>
c) Control: <u>water</u>
d) Constants: <u>amount of toothpaste, kind of toothbrush, how long the toothbrushing took.</u>
Explanation:
In an experiment there usually be independent variable, dependent variable, control gropus, and constants.
The <em>independendent variable </em>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:
<em />
- <em>a. Independent variable (IV): toothpaste brand.</em>
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.
- <em>b. Dependent variable (DV): how much plaque is left.</em>
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.
- <em>c. Control: water</em>
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.
- d. Constants: presumably, the amount of toothpase, the kind of toothbrush, and the time of brushing.
