Z-Score A common statistical way of standardising data on one scale so a comparison can take place is using a z-score. The z-score is like a common measure for all types of data. Each z-score corresponds to a point in a normal distribution. To find a z-score for a specific result in a group of results: First, calculate the Mean for the group. Then calculate the Standard Deviation. Finally, calculate the z-score using the formula: (student result - Mean) / Standard Deviation.