(And how to understand them)(Also called the Normal Curve, or the Gaussian Curve) Below average Above average 50% (i.e., half) score below the mean | 50% or half score above the mean. Colored bell curve courtesy of David W. Stockburger, Introductory Statistics: Concepts, Models, and Applications, http://www.psychstat.smsu.edu/introbook/sbk11m.htm; scales and text added. ____________________________________________ Standard Score (SS) Educational and psychological total
test results are re-expressed in Standard Scores,
where the mean (i.e., average) is set to be 100. In general, the examiner determines the total correct
responses (with or without a correction for guessing) to obtain
a "raw score." The raw score is then converted
to the Standard Score using charts and tables that are provided with each
test.
Scaled Score Scaled Scores
have a mean (or average) score of 10
with
a Standard Deviation of 3. Thus, a Scaled Score
of 13 is ABOVE the AVERAGE. On the WISC-III,
Scaled Scores on the sub-tests are used to make up the total or Composite
Score – on the WISC-III, this is called the Full Scale IQ Score.
Percentile Score Percentile Score* or Rank shows in a more familiar format how the child scored when compared to other children who are the same age or grade. If a child has an IQ of 85, he or she scored at the 16^{th}percentile, which means that 84% of the children tested scored higher than that child. Like Standard Scores, Percentile Scores can be compared from one test to other tests, if each of the tests are Norm-Referenced. *NPR scores are not the same statistically as "percentile." See page 257 of the Home Educators of Virginia Manual for detail.
Stanine Scores essentially represent
Standard Scores, with a range from 1-9. The average (or mean) score
is 5. It is a relatively "coarse" measurement that allows comparison
of scores from one test standardized test to another.
1 2 3 4 5 6 7 8 9
One half of all children tested on a given test will obtain a total test score between the 25^{th} percentile and the 75^{th} percentile. This is considered the "AVERAGE" percentile range.
When your child is tested with standardized
tests, it is very helpful to hand draw a "bell curve" and arrange your
child’s scores along the Standard Score axis (SS number line) to see how
scores have changed from previous test data. Declining scores are
a warning that some adjustments are needed.
Grade Equivalent Score
A child's actual performance on a test -- the number answered correctly and termed a "raw score" -- may be converted to a Grade Equivalent score. The Grade Equivalent score expresses the grade level of students who on average get that raw score. So, for example, if a 3rd grade child who is tested achieves a raw score of 10 points, and children near the end of 1st grade (at the 9th month) on average earn a raw score of 10 points, the 3rd grade child will be assigned a GE score of 1-9 (sometimes written 1.9). "Grade Equivalent scores are based on the assumption that it is helpful to define progress in terms of the grade-level at which an average student attains a given level of knowledge or skill." (www.ets.org/letstalk, p. 3) Age Equivalent Score The Standard Scores can also be statistically converted to show the typical age of the norm group that obtained a similar score. Like the Grade Equivalent Scores, Age Equivalent Scores permit comparison of the child’s scores with those of others who were tested on the same test. Age Equivalent Scores have the same limitations as Grade Equivalent Scores. Additional Information on Test Terms and Skill Remediation http://www.bjup.com/services/testing -- A link for Bob Jones University testing services. A very helpful page with information that will help parents understand the terms used in test reports on their children. The site also provides useful suggestions for addressing skills found to be below average, with specific ideas for remedial actions. |