What is a Zscore?
If you know an individual score ("x"), and compute the mean ("x bar") and the standard deviation ("s"), it is possible to derive standard scores ("z") for any distribution of data. Standard scores are commonly used in mass communication (advertising research), psychology, sociology and education. A zscore allows the comparison of observations obtained by different methods. A standard or "z" score indicates the placement of any score with respect to the mean, in terms of standard deviation above or below the mean. It can be calculated as follows: 

A score of 1.0 tells you that you are "one standard deviation away from the sample mean." Negative scores are "below the mean", positive scores above the mean. Zscores have been computed from the peer evaluation data. 