“Testing, Testing, One…Two…Three!” With the new school year off
and running, we’re all “back to the grind” in our mission to make a difference
for students and the school staff and families who support them. While the majority of
students at school make progress with the traditional approaches presented,
and/or the various supportive interventions offered through the Response to
Intervention (RTI) framework, those with long-term struggles might warrant the
detective work that skilled and seasoned diagnosticians can bring to the table
with comprehensive testing. The goal
being gaining a clearer understanding of the student’s profile of cognitive,
neuropsychological and academic strengths and deficits, allowing us to develop
meaningful educational interventions that school staff and parents can use to
support student growth and success. “What do all those numbers mean?” As skilled, seasoned and committed
clinicians, we not only have a responsibility to get an accurate read on a
student’s cognitive profile, but most importantly, to be able to communicate
what those scores mean for that student’s day to day classroom performance and
prognosis, as they move forward. But all those scores and
numbers can be totally daunting, and even frustrating for parents, teachers and
other school staff bombarded by them. When
looking at the columns of test scores, it’s easy to get overwhelmed!! You’ve
got Raw
Scores, Standard Scores, Percentiles, T scores, Z scores, RPI scores, W scores
and so on. The Normal Curve and the Standard Score Most diagnosticians try and
help others make sense of test scores by plotting a student’s Standard
Score on the Normal Curve, which looks like the
picture below.  The Standard Score tells us
where the student’s performance falls on a particular test measuring that
ability, in comparison to other students their age in the normative sample of students
taking that test. The Mean
is the “Average” score, and Standard Deviation (SD), how far above
or below the Mean a student’s particular score falls. All scores between -1 and +1 SD are considered
to be within the lower and upper ends of Average. As the curve flattens at each extreme (2-3 SD above or below the mean), only a
very small number of students achieve scores at those very low and very high
levels. By plotting a student’s
profile of Standard Scores on various test measures, we can see how they
perform in comparison to others their age. We are also able to compare their
profile of skills relative to one another, providing a picture of their unique
pattern of strengths and weaknesses. "When is the Standard Score NOT the metric of choice?” "Why is my child/student STRUGGLING academically when his or her Standard Scores fall within the “Average Range?” In our over 30 years as School
Psychologists, there were many times we couldn’t explain why students with
Average Standard Scores were still described as struggling by their
teachers and parents, and even found ineligible for specialized services they
truly seemed to require. As School Psychologists, our
responsibility to communicate the meaning of scores, both verbally and in our
reports, may have fallen short when we relied solely on norm referenced Standard
Scores to tell the whole picture.
Those scores served an important role, but seemed inadequate when
needing to describe the nuances of day-to-day academic performance. While appropriate to describe
cognitive sub-skills (e.g. memory, attention, visual perception, reasoning,
etc), Standard Scores may be insufficient measures in some cases.
While Standard Scores and Percentile Ranks describe a student’s relative
standing, or rank order, compared to age or grade peers, they are not
sensitive to the quality of their performance. They are not sensitive to
identifying the nuances of specific learning skills and/or styles of a student’s
performance, which impact their daily performance in school, and their overall
acquisition of academic skills. We now know that more refined
measures may be required to identify the nuances of daily and incremental
growth in academic learning. Here comes the Relative Proficiency Index
(RPI) RPI is a statistical measure that DOESN’T tie into the
Standard Scores or Standard Deviations, and is not generally found on most
tests out there. The Woodcock Johnson Cognitive
and Achievement tests allow for this unique and meaningful measure of progress and
proficiency on tasks that Average peers can perform. The RPI displays how PROFICIENT or FUNCTIONAL a
student is on specific tasks compared to Average peers their
age or in their grade. It indicates the range of development or level of
instruction a student can tackle (independent, instructional, and
frustration levels) and, how EASY or DIFFICULT a task at that level
will be for the student. Although a bit complicated to understand, the
RPI
is represented as a fraction. The
denominator remains at 90, and the numerator ranges from 0-100. Scores range
from 0/90 to 100/90. The student’s expected level of success is
the numerator, and the 90% criterion
is the denominator. For example, an RPI of 60/90 suggests that the student
would be about 60% successful on a task that typical peers would perform with
90% success.
A proficient score (e.g. 96/90) would suggest that
tasks at that level would be EASY for the student to perform. A non-proficient score (e.g. 48/90) would suggest the student likely struggles when tackling tasks at the level most other peers of that age or
grade could manage 90% of the time. A closer look at these Relative
Proficiency Index (RPI) scores is really necessary to better understand
qualitatively
why a child with Standard Scores in the Average range, might be failing
to master academics at an Average level.
It is a more sensitive measure
with implications for classroom performance and really supports what teachers
and parents report! This has strong
implications on many levels, including their importance for consideration at
CSE eligibility meetings! Stay tuned for further
discussions on the W Score as another important statistic. Best, Tina K. Goldman and Roni
Kramer |
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