In Her Treatment Group, Kenesha Had Students with Developmental Disabilities

In her treatment group, Kenesha had students with developmental disabilities swim daily for 20 minutes. In her findings, she reported that at the conclusion of the study, those in the treatment condition had greater self-confidence than those in the no-swimming control group. There were actual differences between groups. Kenesha's conclusion represents

A) a Type I error.
B) a Type II error.
C) both a Type I and Type II error.
D) a correct decision.