The LASS 8–11 reports also provide Stanine scores (ST), National Percentile Ranks (NPR), T-Scores and Z-Scores:
- The Stanine places the student’s score on a scale of 1 (low) to 9 (high) and offers a broad overview of performance.
- The National Percentile Rank relates to the SAS score and shows the percentage of students obtaining a certain score or below. An NPR of 50 is average since 50% of students obtained an SAS of 50 or below. An NPR of 5 indicates that a student’s score is within the lowest 5% of the nationally representative sample and an NPR of 95 means that a student’s score is within the highest 5% of the national sample.
- T-scores have a mean of 50 and a Standard Deviation (SD) of 10, so a T-score of 40 is one SD below the mean and a T-score of 60 is one SD above the mean. 68% of T-scores would fall within the 40-60 range, so a T-score below 40 would be considered below average and a T-score above 60 would be considered above average.
- Finally, Z-scores show us the student’s score in standard deviation units, with a mean of 0 and an SD of 1. So, a Z-score of -1.0 would indicate that the student’s score is one SD below the mean and a Z-score of +1.0 would indicate that the student’s score is one SD above the mean.
The relationships between these different scores are shown in Figure 27 below.
Figure 27. Relationship between scores