In an In-Class Demonstration of a Classic Experiment on the Effects

In an in-class demonstration of a classic experiment on the effects of smiling on happiness, an instructor had students sitting on the left side of the classroom read a series of cartoons while frowning and had students sitting on the right side of the classroom read the same series of cartoons while smiling.In this example, the instructor failed to:

A) obtain a small sample size.
B) randomly assign participants to conditions of the study.
C) recruit a convenience sample.
D) calculate the subjective probability of group membership.