Variables

1. Variables EQ: Why is it important to alter only one variable in an experiment?

2. Test Variable • a.k.a. independent variable or manipulated variable • Factor which is changed in an experiment • Ex. In an experiment to determine the amount of water a plant needs to grow tallest, one might water one plant daily, one weekly, and one monthly. The test variable is how often the plant is watered. • P.S. Graphed on the x axis

3. Outcome Variable • a.k.a. dependent variable or responding variable • Factor which is observed or measured; the data your are collecting • Ex. In the previous experiment, the outcome variable would be how tall each plant has grown. • P.S. Graphed on the y axis

4. Control Group • Experiments are run with an experimental group and a control group. • The experimental group receives treatment. • The control group receives no treatment. They give you something to compare your results to. • In our example, the control group would receive no water while the experimental group(s) would receive water (the test variable).

5. Constants • Factors that are held the same in an experiment. • Ensure that only one factor is changed in an experiment (the test variable). • Everything else is identical, the constants. • Ex. In the previous experiment, we would use identical plants, pots, soil, amount of sunlight, and amount of water.