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
Powerpoint
(In Class)
Password: knights
