Interpreting Test Scores
Parents need to understand some of the important concepts about interpreting the statistical test data on the assessments given. Here is the essential information parents should know about understanding test data:
- Usually, overall information is presented in Standard Scores, which have a mean of 100 and a standard deviation of 15. That means a standard score of 100 is exactly average. The majority of the population (68%) will score within 15 points of the mean (100). Most of the students in a class will score between 85 and 115 on an assessment. The further away from 100 someone scores, the more atypical it is. For example, approximately 3% of the population is considered truly gifted (an IQ above 130 versus an average IQ of 100).
- Sometimes T-Scores are used, especially with Behavior Rating Scales. These have a mean of 50 and a standard deviation of 10. This means that anything between 40 and 60 is normal. The further a score falls from 50, the more atypical it is. If a student is rated with a T-Score of 75 in depression on a rating scale, this means that the student is showing significant symptoms of depression.
- Percentiles do NOT mean what percentage of the questions the student got correct. It is a statistical term that indicates how well she did compared to other students the same age. For example, an average score of 100 is at the 50th percentile. This means that 50 percent of students the same age did better and 50 percent did worse. If a score is at the 23rd percentile, she performed better than 23 percent of students her age.
- Grade equivalents can be very misleading and parents should not put too much stock in them.