What are the similarities and the differences between a T score and a z score?
Both T scores and z scores are standard scores, that is, they are based on the standard deviation, or how widely scores vary from the mean. T scores have a mean of 50 and a standard deviation of 10. Z scores indicate the number of standard deviations above or below the mean. For example, if a score was one standard deviation below the mean it would have a z score of -1 (one standard deviation below the mean, in which the mean value is 0) and a T score of 40 (a mean of 50 minus 10, one standard deviation, equals 40).
