Norm-referenced tests compare an individual child's
performance to that of his or her classmates or some other, larger
group. Such a test 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
Percentiles are probably the most commonly used test score in education.
A percentile is a score that indicates the rank of the student compared
to others (same age or same grade), using a hypothetical group of
100 students. A percentile of 25, for example, indicates that thestudent's
test performance equals or exceeds 25 out of 100 students on the
same measure; a percentile of 87 indicates that the student equals
or surpasses 87 out of 100 (or 87% of) students. Note that this
is not the same as a "percent"-a percentile of 87 does
not mean that the student answered 87% of the questions correctly!
Percentiles are derived from raw scores using the norms obtained
from testing a large population when the test was first developed.
are essentially groups of percentile ranks, with the entire group
of scores divided into 9 parts, with the largest number of individuals
falling in the middle stanines (3-7), and fewer students falling
at the extremes. Few tests in common usage today use stanines, although
these scores can be useful in understanding the relative range of
a student's performance.
A standard score is also derived from raw scores using the norming
information gathered when the test was developed. Instead of reflecting
a student's rank compared to others, standard scores indicate how
far above or below the average (the "mean") an individual
score falls, using a common scale, such as one with an "average"
of 100. Standard scores also take "variance" into account,
or the degree to which scores typically will deviate from the average
score. Standard scores can be used to compare individuals from different
grades or age groups because all scores are converted to the same
numerical scale. Most intelligence tests and many achievement tests
use some type of standard scores. For example, a standard score
of 110 on a test with a mean of 100 indicates above average performance
compared to the population of students for whom the test was developed
Age/Grade Equivalent scores.
Some tests provide age or grade equivalent scores. Such scores indicate
that the student has attained the same score (not skills) as an
average student of that age or grade. For example, if Sally obtains
a grade-equivalent score of 3.6 on a reading comprehension test,
this means that she obtained the same score as the typical student
in the sixth month of third grade. Sally may or may not have acquired
the same skills as the typical third grader. Age/grade scores seem
to be easy to understand but are often misunderstood, and many educators
discourage their use.
Standard scores, percentile ranks, and stanines
can be compared using the "normal" or bell-shaped curve.
Most tests used in education are developed in order to yield a standard
curve of scores, where the majority of all students would fall within
a small range (or one "standard deviation") of the mean
or average score, and where 50% of all students would fall above
and 50% would fall below the average score. Some tests, however,
do not have such "normal" distributions of scores, and
these different types of scores may not be comparable.