Science Experiments: Variables

When scientists do experiments, they want to learn how things work. They change things to see what happens. These things that can be changed are called variables. Knowing about variables helps scientists make good guesses and test them.

There are three main types of variables: independent, dependent, and controlled. The independent variable is the thing that the scientist changes on purpose. It's like the thing you are testing. For example, you might change the amount of water you give to different plants. The amount of water is the independent variable.

The dependent variable is what you measure to see if it changes when you change the independent variable. It's what you are testing. In the plant example, the height of the plants would be the dependent variable. The plant's height might change depending on how much water it gets.

Controlled variables are things that you keep the same during the experiment. This is important because you want to make sure that only the independent variable is affecting the dependent variable. For the plants, you would want to make sure all the plants get the same amount of sunlight and the same kind of soil.

Here's another example. Imagine you want to see if the brightness of light affects how moths are attracted to it. The brightness of the light is the independent variable because you can change it. How close the moth gets to the light is the dependent variable because that's what you measure. You would need to control other things, like the type of light bulb, so only the brightness is different.