Discussion:
Q: A psychologist conducts a study of perceptual illusions under two different lighting conditions. Twenty participants were each tested under both of the two different conditions. The experimenter reported: "The mean number of effective illusions was 6.72 under the bright conditions and 6.85 under the dimly lit conditions, a difference that was not significant, t(19) = 1.62." Explain this result to a person who has never had a course in statistics. Be sure to use sketches of the distributions in your example.