To understand this difference, we must first define an extraneous variable. There are three primary types of variables in an experiment: dependent, independent, and extraneous. The independent variable is changed to study the resulting change in dependent variable. However, extraneous variables also will impact the dependent variable. For instance, when studying shark bite rates by month, an extraneous variable would be the temperature of the water—because less people would be likely to be in the water and therefore be bit.
A confounding variable is a type of extraneous variable, but it additionally will change along with the independent variable. In the situation above, water temperature will fluctuate with month, so it is intricately linked with the independent variable and is therefore a confounding variable.
A confounding variable is one kind of extraneous variable.
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