1. When given a raw score, it must be converted into a z-score (standard score). Raw scores cannot be placed on a normal distribution curve because they do not have the same means and standard deviations, but when it is converted into a z-score, the number of standard deviations above or below the population mean can be measured. The z-scores on the center are average, the scores on the left are lower than average and the scores on the right are higher than average.
2. A z-score is a standard score which can be placed on a normal distribution curve. A z-score indicates the distance of the standard deviations from the mean (center of the curve).