In educational research, test scores are often summarized as if they emerge from a normal distribution. Such a distribution can be described by two parameters: the center (measured by the mean) and dispersion (measured by the variance or standard deviation). This article summarizes the most commonly used measures of dispersion: several types of range statistics, standard deviation, variance, and median absolute deviation. Their strengths and limitations are discussed. Two additional concepts – skewness and kurtosis – are discussed as a way to test normality of the distribution, as well as to describe departures from normality.