Independent and Dependent Variables
In the ice cream example, we discussed how changes that we make may result in other changes. During an investigation, often times one thing being changed also responds in another result. Using our example, the softness of the ice cream responded to changes in the temperature of the freezer. A variable that we purposefully change or manipulate is called the independent variable. The thing that changes in response is called the dependent variable. This creates a cause and effect relationship. To have a fair test, always have only one independent variable at a time in your investigation.
You can remember these by thinking of the independent variable as the “I changed it” variable, and the dependent variable as the “what changed?” variable. Remember the “I” in “I changed it” is like the “I” at the beginning of the word independent. This will help you remember the difference between these two types of variables.
Using our ice cream and the freezer temperature example, which is the independent variable? Which is the dependent variable?
Remember, we listed several possible factors that may contribute to the softness of the ice cream. We tested the freezer temperature factor, but any of the other factors might also be affecting the softness of the ice cream. In a scientific investigation, always be sure to test each of the possible factors before concluding your work. You may find that one factor has a stronger influence than others, or that several factors work together.
Freezer at -15° C (5° F) Freezer at 0° C (32° F) Freezer at 15° C (59° F)
Keep track of the independent variable and its affect on your dependent variable each time you test something. Also, remember to only test one possible factor at a time and keep all other factors constant each time you conduct a test.