In an experiment, a psychologist has to consider all the variables that are involved that can affect the results, either intentionally or unintentionally, within the experiment.
A variable is something that can change and potentially affect the results of an experiment. These are the causes and effects that are being manipulated and measured inside the experiment.
EXAMPLEFor example, suppose an experiment is measuring the effect of sleep on intelligence, as measured by test scores. The variables would be the amount of sleep that the subjects get and their intelligence as measured on the test score. These are the two variables to consider within that experiment.
There are different types of variables that a scientist needs to consider to determine the accuracy of an experiment itself:
EXAMPLEGoing back to the example above of the experiment measuring sleep and its effect on intelligence, the independent variable would be the amount of sleep. This is the variable that can be changed, to see what the results would be.
EXAMPLERecall, in the sleep experiment, sleep was the independent variable, which would mean the dependent variable--the result of the amount of sleep--would be the intelligence of the subjects that is tested.
Typically, dependent variables are measured by something very specific or concrete--like intelligence measured by test scores--because research relies on scientific measures.
Lastly, there are extraneous variables, which are any outside variables or conditions that might affect the results of the experiment.
Therefore, the experimenter needs to recognize that these different extraneous variables might have an effect and design their experiment to control for them, so they don't influence the experiment.
EXAMPLEThe experimenter in the sleep study might choose people that are at a similar level of intelligence, so there aren't any differences in their test scores. Or, they might give everybody participating in the experiment the same thing to eat the night before, so that this variable doesn't affect the true results of the experiment.
It is also important to consider extraneous variables when analyzing the data and recognize when there are different or outlying results that might be the effect of extraneous variables.
Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR ERICK TAGGART.