Variables are conditions that could affect the outcome of an experiment. For instance, think about all of the different
things that might affect how well a student does on a test. Their amount of sleep, how long they studied, how well they
paid attention in class, if they’re feeling well, the behavior of the students around them, if they’re having trouble at
home or they don’t like the teacher…all of these things, and more, could affect how well that student performs.
Develop at least 3 variables for each of the following situations.
A) What variables can affect the number of fish in a lake?
B) What variables can affect the speed of a runner in a 100-yd dash?
C) What variables can affect attendance at a baseball game?
D) What variables can affect the taste of soda?
E) What variables can affect the amount of fruit an apple tree produces?
F) What variables can affect student performance on a social studies quiz?
It is important to identify the variables in any experiment. You want to have as few variables as possible when
conducting your experiment, but you will always have three types of variables, independent, dependent, and constant
(also called control).
The independent variable is WHAT YOU CHANGE ON PURPOSE IN AN EXPERIMENT.
The dependent variable is WHAT YOU MEASURE IN AN EXPERIMENT.
The control variable is the condition or conditions that REMAIN THE SAME in an investigation. You have to have
controlled variables so that you can determine if the independent variable actually caused the result, or if it was
something else.
Consider the following experiments:
A) Two groups of students were tested to compare their speed working math problems. Each group was given the same
problems. One group used calculators and the other group computed without calculators.
What is the independent variable?
What is the dependent variable?
What is the constant variable?
B) Students of different ages were given the same puzzle to assemble. The assembly time was measured.
What is the independent variable?
What is the dependent variable?
What is the control variable?
Assignment:
1. Smithers thinks that a special juice will increase the productivity of workers. He creates two
groups of 50 workers each and assigns each group the same task (in this case, they're supposed to
staple a set of papers). Group A is given the special juice to drink while they work. Group B is not
given the special juice. After an hour, Smithers counts how many stacks of papers each group has
made. Group A made 1,587 stacks, Group B made 2,113 stacks.
Identify the:
1. Control Group
2. Independent Variable
3. Dependent Variable
4. What should Smithers' conclusion be?
5. How could this experiment be improved?
2. Homer notices that his shower is covered in a strange green slime. His friend Barney tells him
that coconut juice will get rid of the green slime. Homer decides to check this this out by spraying
half of the shower with coconut juice. He sprays the other half of the shower with water. After 3
days of "treatment" there is no change in the appearance of the green slime on either side of the
shower.
6. What was the initial observation?
Identify the:
7. Control Group
8. Independent Variable
9. Dependent Variable
10. What should Homer's conclusion be?
3. Bart believes that mice exposed to radio waves will become extra strong (maybe he's been
reading too much Radioactive Man). He decides to perform this experiment by placing 10 mice
near a radio for 5 hours. He compared these 10 mice to another 10 mice that had not been
exposed. His test consisted of a heavy block of wood that blocked the mouse food. He found that
8 out of 10 of the radio-waved mice were able to push the block away. 7 out of 10 of the other
mice were able to do the same.
Identify the:
11. Control Group
12. Independent Variable
13. Dependent Variable
14. What should Bart's conclusion be?
15. How could Bart's experiment be improved?
4. Krusty was told that a certain itching powder was the newest best thing on the market; it even
claims to cause 50% longer lasting itches. Interested in this product, he buys the itching powder and
compares it to his usual product. One test subject (A) is sprinkled with the original itching powder,
and another test subject (B) was sprinkled with the Experimental itching powder. Subject A reported
having itches for 30 minutes. Subject B reported to have itches for 45 minutes.
Identify the:
16. Control Group
17. Independent Variable
18. Dependent Variable
19. Explain whether the data supports the advertisements claims about its product. - It does