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Background: When conducting experiments, one needs to deal with variables, those factors or elements that are likely to vary or change.
A typical study has an independent variable and a dependent variable.
Let's say you wish to learn which type of fertilizer will make your plants grow the tallest. You have fertilizer A, B, and C.
The independent variable is the type of fertilizer.
The height of the flowers = dependent variable.
The flowers with no fertilizer are the control group.
Data Table
Data Table
The independent variable is on the left side of a data table.
The trials and the averages are the dependent variable, or results.
Independent Variable
The independent (or manipulated) variable is something that the experimenter purposely changes or varies over the course of the investigation.
In this case the experimenter is changing the type of fertilizer.
Think: "I change" → Independent.
In general, scientists only investigate one independent variable at a time.
Dependent Variable
The dependent (or responding) variable is the one that is observed and likely changes in response to the independent variable. This is the factor that is measured or observed. This variable shows results.
Think: "Depends on" → Dependent.
In this example, the dependent variable is the height of the flower.
Controlled Variables! (Constants)
When conducting an experiment, all other variables must be kept the same throughout the investigation; they should be controlled - so the test is fair. The variables that kept the same are called controlled variables. These variables are kept constant. Think: "Control = Keep constant."
In the plant study, all flowers should get the same amount of water, the same amount of light and should also be kept at the same temperature. These are controlled variables.
Experimental Group
In an experiment, group that is exposed to the independent variable is called the experimental group. The experimental group is also sometimes called the treatment group.
Control Group
The control group is not exposed to the independent variable. The control group is unmodified. It is left in its normal state. (Do not confuse controlled variables with the control group.) The control group used in an experiment for comparison purposes.
The flowers that did not receive fertilizer would be the control group.
👉 A quick way to remember:
Independent = I change. Independent starts with "I", like Roman numeral 1.
Dependent = Data I collect
Controlled = Kept constant
Experimental Group = is experimented on
Control Group = Comparison group
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