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.
The solution provides step by step method for the calculation of test statistic. Formula for the calculation and Interpretations of the results are also included.