PURPOSE: In this activity, you will practice graphing the results of an experiment. You will also learn what constitutes a valid experimental procedure.

Question

PROBLEM: How many drops of water will fit onto the “Lincoln” side of a penny?
PREDICTION (Hypothesis): I predict that ____ drops of water will fit on the head side of a penny.

A constant is things in an experiment that are kept the same in all trials.

1. In this experiment, there were a limited number of constants. Name two of them.

An independent variable is changed on purpose by the experimenter.

2. What was the independent variable in this experiment?
3. Where is the independent variable located on a graph?

A dependent variable is a variable that responds to the independent variable.

4. What was the dependent variable in this experiment?
5. Where is the dependent variable located on a graph?

A control variable is a test group that does not receive the independent variable.

6. Based on this experiment, is there a control group present? If so, what is it?

Validity is a measure of how correct the results of an experiment are. Think about what makes an experiment valid.

7. Using your bar graph, determine if the average number of drops for each group is about the same. List four reasons why the actual number of drops for each group was similar or dissimilar.
8. Are the results of this experiment “valid”? Why or why not?
9. What would happen if you used the other side of the penny? When comparing data with the rest of the class, why would it be important that we all use the same “Lincoln” side of the penny?

Answer 1

7. The average number of drops for each group is similar because:
a) All trials were conducted with the same type of penny.
b) All trials were conducted by using the same procedure.
c) The same type of water dropper was used for all trials.
d) The same amount of time was given for the drops to be added.

8. The results of this experiment are "valid" because all the necessary controls were in place. The experiment was conducted in a consistent manner, with the same conditions for each trial.

9. If the other side of the penny was used, it may affect the results as the texture and surface properties of the two sides could be different. It is important that we all use the same "Lincoln" side of the penny to ensure consistency and comparability of the data across different experiments.