A class of twenty third graders has been taught reading for the past three years using the McNeil Method. The class mean is 70.5 with a variance of 121. Thus, it is concluded that the class of third graders scored significantly higher than the state average. The ability of a statistical test to yield meaningful results when the data fail to meet underlying assumptions of the test. If data are clearly nonnormal or if outliers are present, do not use t-distribution.
Observations are independent of each other.
Insured by SRS and random assignment of subjects to groups. Observations are sampled from normal populations. Observe histograms for each group. Homogeneity of Variance. Samples come from populations with equal variances.