Racial classifications or groupings are of various types. Therefore, the sentence above is on the basis of extraneous variable.
Extraneous variable
In an experiment, an extraneous variable is any variable that one is not investigating that can potentially affect the outcomes of one's research study. If left uncontrolled, extraneous variables can lead to inaccurate conclusions about the relationship between independent and dependent variables.
Therefore, the above is an instance of an extraneous variable.
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