A z-score is a statistical measurement that tells you how many standard deviations a specific point is away from the mean of a distribution. It’s used to compare scores from different tests or data sets, even if they have different scales. In analyzing test scores, a z-score helps you see how a particular score compares to the average test performance. A high positive z-score indicates a much higher score than average, while a negative z-score indicates a score lower than the average.