If Possible, the Experimenter Who Manipulates the Independent Variable Should

Multiple Choice

If possible, the experimenter who manipulates the independent variable should not also administer the measure of the dependent variable because

A) these two tasks require different talents, and few people are able to perform both adequately.
B) a single person performing both tasks decreases experimenter realism.
C) a single person performing both tasks decreases external validity.
D) a single person performing both tasks increases the likelihood of experimenter expectancy effects.