Which of the following is NOT a source of confounding variables?

A) random assignment
B) selection bias
C) placebo
D) experimenter bias

Confounding Variables

Factors other than the independent variable(s) that are unequal across groups.

Random Assignment

A method used in experiments to ensure that every participant has an equal chance of being assigned to any given group, thereby reducing bias.

Experimenter Bias

A phenomenon that occurs when a researcher’s preconceived notions or expectations in some way influence participants’ behavior and/or the researcher’s interpretation of experimental results.