# Independent and Dependent Variables Scenarios

## (Manipulated and Responding)

### Scenarios

For each, identify the independent (manipulated) and dependent (responding) variable.

1.  A cow is given a growth hormone and then compared to another cow that was not given a growth hormone.  Both cows were weighed at 2 years.

2.  Mosquito repellent is sprayed on one arm and the other arm is not sprayed.  The number of mosquito bites is counted after 2 hours.

3.  One grape is placed in tap water and another grape is placed in salt water. The change in their mass is measured after a day.

4.Two different cars are traveling at 60 mph.  At a certain point, both cars slam on the brakes.  The distance it takes for each car to stop is then measured.

5. Pillbugs are placed in a container where they have a choice of a wet or a dry environment.  Researchers record how much time was spent on each side.

6.  A stapler is used to staple 100 papers, it jams 5 times during the trial. A different brand of stapler performs the same test; it jams 22 times.

7. Cockroaches are exposed to a pesticide.  After 3 hours, 95% of the insects are dead.

8. Two plants are grown using the same light and pots.  One plant is given water that has been microwaved and the other plant is given regular tap water.  Their height is measured after 2 weeks.

9. The blood pressure of a soldier is measured while he is resting.  The soldier is then exposed to a stressful environment and his blood pressure is measured again.

10.  An apple is cut into slices. Half of the slices are sprayed with lemon juice. All slices are stored in a sealed plastic bag. After 4 days, they are observed to see how brown they turned.

11. The respiration rate of a goldfish is measured. The goldfish is then placed in cold water and the respiration rate is measured again.

12. Bacteria are grown in a petri dish. One side of the dish is sprayed with an antibiotic.  After a week, the number of bacteria colonies are counted on each side.

## Other Resources on the Scientific Method

Variables with Simpsons – read stories involving characters from the Simpsons and determine the independent and dependent variables

Beriberi and Penicillin – a short story on the discovery of penicillin and that Beriberi was caused by a vitamin deficiency

Discoveries in Science – focus on Pasteur’s experiment and other discoveries in science

Scientific Method Scenarios – activity where students are given a question and must design an experiment and identify variables