13
Understanding Test Scores
Norm-Referenced Tests. Normed reference tests compare an individual child’s performance to
that of his or her classmates or some other, larger group. The WISC-V was normed on 2,200
children while the WJ IV was normed on over 7,000 children. Such tests will tell you how your
child compares to similar children on a given set of skills and knowledge, but it does not
provide information about what the child does and does not know. Scores on norm-
referenced tests indicate the student’s ranking relative to that group. Typical scores used with
norm-referenced tests include:
Standard Scores. A standard score is derived from raw scores using the norming information
gathered when the test was developed. Standard scores indicate how far above or below the
average an individual score falls using a common scale with a mean of 100. The WISC-V Index
scores, WJ IV subtest and cluster scores all are reported via standard scores. Scores from 90 –
110 are considered in the average range.
Percentiles. A percentile is a score that indicates the rank of the student compared to others
(same age or same grade). An average standard score of 100 would fall at the 50
th
percentile.
This indicates the child’s performance equals or surpasses 50% of his/her peers from the
standardization group. A percentile is not the same as a percent – a percentile does not mean
that the student answered 50% of the questions correctly. Percentiles from 25 to 75 are
considered in the average range.
Scaled Scores (WISC-V subtests only). Psychoeducational tests are typically made of several
mini-tests, or subtests, which assess more specific skill sets. Performance on each subtest
results in a scaled score ranging from 1 to 19. Scale scores are often combined to form
standard scores. On the WISC-V, scaled scores from 8 to 12 are considered in the average
range.
Qualitative Descriptors. Qualitative descriptors are quick ways to report the interpretation of
the scores in relation to similar peers, such as Low Average, Average, and High Average. Each
normed referenced test has separate guides on applying qualitative descriptors.
Confidence Intervals. Since a child’s performance on a test can vary on any given day, the
confidence interval is the hypothetical range of scores predicted if your child were given this
test 100 times. For example, a 95% confidence interval means there is a 95% likelihood that
your child would score in the given range if administered the test 100 times.