VARIABLES

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VARIABLES CONTROLS

• Scientists use an experiment to search for cause
  and effect relationships in nature.
• In other words, they design an experiment so that
  changes to one item cause something else to vary
  in a predictable way.

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Variables are things that vary and change
A variable is any factor, trait, or condition
that can exist in differing amounts or types.
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Variables

• In any experiment there are 2 variables
• an independent (or input) variable
• a dependent (or outcome) variable
• Lets look at each type.

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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.

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Independent (input) variable
This is the thing that you decide to
change. Example
Investigating how a weight affects the length of
an elastic band.
You decide the weight to apply, so Weight is
the independent variable.
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dependent variable

• This is what the scientist focuses his or her
  observations on.
• This is to see how it responds to the change made
  to the independent variable.
• The new value of the dependent variable is caused
  by and depends on the value of the independent
  variable.

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Dependent (outcome) variable
This is the variable that changes as a result of
the independent variable.It is the variable that
you measure. Example
Investigating how a weight affects the length of
an elastic band.
You measure the resulting length of the elastic
band, so Length is the dependent variable.
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• if you open a faucet (the independent variable),
• the amount of water flowing (dependent variable)
  depends on how much more you open the faucet

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Controls

• Experiments also have a control.
• Controls are amounts that a scientist wants to
  remain constant, and she must observe them as
  carefully as the dependent variables.

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Controls
These are all the things that must NOT change, to
make sure it is a fair test. Example
Investigating how a weight affects the length of
an elastic band.
You must use the same elastic band all the time,
and the same scale etc,so it is a fair test.
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In Summary
Example 1
The independent variable is?

• weight

The dependent variable is?

• length of the elastic

The control variables are?
same elastic band,same scale, etc,so it is a
fair test.
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Variables have to be measurable.

• In a good experiment, the scientist must be able
  to measure the values for each variable.
• Weight or mass is an example of a variable that
  is very easy to measure.
• Imagine trying to do an experiment where one of
  the variables is love. There is no such thing as
  a "love-meter."
• You might have a belief that someone is in love,
  but you cant really be sure. Some of your
  friends wouldnt agree with your belief.
• Love is not measurable in a scientific sense
  therefore, it would be a poor variable to use in
  an experiment.

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Simpsons activity

• You will have class work, if you dont finish it
  in class it will then be homework! ?