What is a variable A variable is anything

�What is a variable? �A variable is anything that can affect the results in an experiment.

� How do variables in an experiment work? � In order to have a reliable experiment, you can only change ONE thing we are testing! � If we change more than one thing, we will not know why the experiment worked the way it did.

Type of plant Type of fertilizer Fern � We Amount of water Amount of sunlight Height of plant Miracle Grow 10 m. L 5 hours 5. 7 cm Speedy Grow 10 m. L 5 hours 3. 4 cm are testing two types of fertilizer (miracle grow and speedy grow) to see which plant grows the tallest. � We will use the same plant, the same amount of water, and the same amount of light. � The ONLY variable we change or that is different is the type of fertilizer! � Since we don’t change anything else, we can see the affect the fertilizer has on the plants.

Type of plant Type of fertilizer Fern Spider plant � We Amount of water Amount of sunlight Height of plant Miracle Grow 10 m. L 5 hours 5. 7 cm Speedy Grow 10 m. L 5 hours 3. 4 cm are testing different fertilizers to see which one makes the plant grow the tallest. � The amount of water and sunlight are the same. � The type of fertilizer AND the type of plant are different. � Since there is more than one variable different, this experiment is not reliable or valid. We don’t know which variable (fertilizer or plant) affected the growth.