Interpreting TerraNova Scores
By Inderbir Kaur Sandhu, Ph.D
Q:
I am not familiar with how to interpret the test results
from the TerraNova. Can you please tell me what the
"average" score would be? Also, the scores are abbreviated
as NP, NS, NCE, SS. Would you also please clarify what each
of these mean. NP-National Percentile? SS-Standard Score? I
have to look at these scores in order to decide on the
correct placement level for high school students. I hope you
can help.
A: Unfortunately, I am only
familiar with the TerraNova based on reading and available
information - I have not administered this test.
I would try to help you with the information I have on NP,
NS, NCE and SS.
National Percentiles (NP)
Represents the percentage of students in the national norm
group whose scores fall below a given student's score. This
means, a student whose NP is 72 for instance, scored higher
than 72 percent of the students in the norm group. NPs
scores are useful for comparing local student achievement to
students' achievement at the national level.
National Stanine (NS)
A scale that divides the scores of the norming sample into
nine groups ranging from a high of 9 to a low of 1. Stanines
are normalised scores that have a constant relationship to
Percentiles. That is, a given Percentile always falls into
the same Stanine. Stanine 5, for example, always includes
Percentiles 41-59. Stanines are single digit scores and are
not likely to be confused with percentage of items answered
correctly, and they can be averaged because they are equal
interval scores. However, Stanines provide less detail about
student performance than other derived scores because they
categorise test performance into only nine broad units.
Normal Curve Equivalent (NCE)
This curve was designed to be used in the evaluation of
compensatory education and other special programmes. The
range is from 1 to 99 and coincide with the NP scale at 1,
50, and 99. NCEs are normalised equal interval scores and
are not recommended for use in reporting individual student
scores since the NCE is easily confused with the NP.
Scale Scores (SS)
The Scale Score is the basic score for TerraNova and other
CTB assessments. It is used to derive all the other scores
that describe test performance. Scale Scores can be obtained
by one of two scoring methods. The first is Item Response
Theory (IRT) item-pattern scoring, a procedure offered only
by CTB among the major K-12 test publishers. With
item-pattern scoring, Scale Scores are derived numerically
using all the information contained in a student's pattern
of item responses. The second method is number correct
scoring. This method converts the number of correct
responses (or points earned for constructed-response items)
to a Scale Score. For groups of 25 or more students, the
item-pattern and number-correct Scale Scores produce
equivalent results. Customers can choose to use either
scoring method. CTB recommends item-pattern scoring because
it provides more accurate results for individual students.
Scale Scores are equal-interval scores that can be averaged
and used in other statistical analyses.
A very informative site for information on interpretation of
the scores can be found here:
Guide to Test Interpretation: The Alaska Norm-Referenced
Test
Hope that helps!
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