There are three main types of variables: independent, dependent, and controlled. Let's learn about each one.
Independent Variables
The independent variable is the factor that the scientist changes. What was different about the ice cream in our experiment? The flavor. You, the scientist, changed which flavor was put in each bowl.
Independent variables stand alone because they are not influenced, or changed, by anything else in an experiment.
Dependent Variables
The dependent variable is what is being measured in an experiment. It's called 'dependent' because it depends on the independent variable.
In our experiment, we measured how long it took each scoop of ice cream to melt. In this experiment, the time it takes a scoop to melt is dependent on the flavor of the ice cream.
Controlled Variables
In an experiment, the only thing that should be changing is the independent variable. All other variables have to be the same. Controlled variables are all the other variables that a scientist must make sure are the same throughout the entire experiment.
Our experiment was all about different ice cream flavors - our independent variable. We wanted to know how the flavors affected the melting time. So, other than the experimenter changing the flavors, everything else must stay constant.
In our experiment, what else could be different about the conditions of the scoops besides their flavor? You could put two scoops of chocolate ice cream in a bowl but use only one scoop of the other flavors. One bowl could be placed in the sun and the others in the shade. You could even put the scoops in different types of bowls. If any of these conditions were not exactly the same for each ice cream flavor, when you measure how long it takes the scoops to melt, you could not be certain that flavor was the only reason some scoops melted faster than others.
So, you have to control all of the variables in an experiment (except for the independent variable). Only when you are certain that all variables are the same can you know that the results of your experiment are accurate.
