Stephanie Conducts an Experiment to Learn If Brunettes Have More

Multiple Choice

Stephanie conducts an experiment to learn if brunettes have more fun. She has three brunette female friends and three blonde female friends go to the same party and record how many times they are asked to dance. When Stephanie discovers that two of the three brunette friends in her experiment are terrible dancers, she realizes that her results may be invalid due to

A) a poor manipulation.
B) a confounding variable.
C) a fourth variable.
D) the lack of redheads in the study.