What are Independent and Dependent Variables?
Question: What's a variable?Answer: A variable is an object, event, idea, feeling, time period, or any other type of category you are trying to measure. There are two types of variables-independent and dependent.
Question: What's an independent variable?
Answer: An independent variable is exactly what it sounds like. It is a variable that stands alone and isn't changed by the other variables you are trying to measure. For example, someone's age might be an independent variable. Other factors (such as what they eat, how much they go to school, how much television they watch) aren't going to change a person's age. In fact, when you are looking for some kind of relationship between variables you are trying to see if the independent variable causes some kind of change in the other variables, or dependent variables.
The independent variable is the one that is changed by the scientist. To insure a fair test, a good experiment has only one independent variable. As the scientist changes the independent variable, he or she observes what happens.
Question: What's a dependent variable?
Answer: Just like an independent variable, a dependent variable is exactly what it sounds like. It is something that depends on other factors. For example, a test score could be a dependent variable because it could change depending on several factors such as how much you studied, how much sleep you got the night before you took the test, or even how hungry you were when you took it. Usually when you are looking for a relationship between two things you are trying to find out what makes the dependent variable change the way it does.
Many people have trouble remembering which is the independent variable and which is the dependent variable. An easy way to remember is to insert the names of the two variables you are using in this sentence in they way that makes the most sense. Then you can figure out which is the independent variable and which is the dependent variable:
(Independent variable) causes a change in (Dependent Variable) and it isn't possible that (Dependent Variable) could cause a change in (Independent Variable).
For example:
(Time Spent Studying) causes a change in (Test Score) and it isn't possible that (Test Score) could cause a change in (Time Spent Studying).
We see that "Time Spent Studying" must be the independent variable and "Test Score" must be the dependent variable because the sentence doesn't make sense the other way around.
Experiments also have controlled variables. Controlled variables are quantities that a scientist wants to remain
constant, and he must observe them as carefully as the dependent
variables. For example, if we want to measure how much water flow increases
when we open a faucet, it is important to make sure that the water pressure
(the controlled variable) is held constant. That's because both the water
pressure and the opening of a faucet have an impact on how much water flows. If
we change both of them at the same time, we can't be sure how much of the
change in water flow is because of the faucet opening and how much because of
the water pressure. In other words, it would not be a fair test. Most
experiments have more than one controlled variable. Some people refer to controlled variables as
"constant variables."
Tutorial
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