Transformation Rules Learn how to calculate means and standard deviations if data are simply transformed. Z scores are very important position measures. Z scores use standard deviations that you learned to calculate in Chapter 5 in their formula. You will need to pay particular attention to the calculation and understanding of z scores. Z scores tell how many standard deviations away from the mean a score resides.
Z scores can be positive or negative.
A positive z score indicates that the value is above the mean. A negative z score indicates that the value is below the mean. The two equations on the left are used to calculate z scores. The first equation is for populations. In the first equation the Greek letters mu and sigma stand for the population mean and standard deviation.