Employee Survey Benchmark Scoring - T-Scores Explained

Raw Scores are simply an average of all responses. With a 5-point rating scale, the lowest possible raw score is a 1, and the highest possible raw score is a 5.

By themselves, raw scores do not give any indication of whether a score is high or low. T-Scores make this possible by eliminating the natural variations between items and providing a benchmark to measure the raw scores by.

T-Scores show how your scores compare to the scores received by other organizations. When using T-Scores, the mean (average) is always 50, and the standard deviation is 10. If your T-Score is above 50, then it is above average. If your score is less than 50, it is below average. For example, if you have a T-Score of 60, you scored higher than 84% of all organizations. T-Scores are distributed in a bell-shaped curve, as illustrated in the diagram to the right. 68% of T-Scores fall between 40 and 60. 96% of scores fall between 30 and 70. Only 4% of scores fall below 30 or above 70.

In order to calculate T-Scores, we need to start with good normative (benchmark) data. This is obtained by collecting survey responses from employees at hundreds of different organizations. We then calculate the average (mean) and the standard deviation of the scores for each survey item across all those organizations. (Standard deviation is a measure of variation. It indicates how much scores vary across different organizations.)

To calculate a T-Score, we take your organization's raw score minus the normative mean (average across all organizations) and divide by the standard deviation. Lastly, we multiply by 10 and add 50. (These last steps simply transform the score into a range that is more intuitive. If we omit these last steps, the score is referred to as a z-score, with an average of zero and a standard deviation of 1.)

In other words: