formula for z statistic
Use the following format to find a z-score: z = X - Î¼ / Ï. This formula allows you to calculate a z-score for any data point in your sample. 1  Remember, a z-score is a measure of how many standard deviations a data point is away from the mean.2  In the formula X represents the figure you want to examine.his will start out the calculations for a z-score. 1  For example, in our sample of tree heights we want to find out how many standard deviations 7.5 is from the mean of 7.9. 2  Therefore, you would perform the following: 7.5 - 7.9.