Why Measure Growth
• Student learning is a central goal of
education
• Assessments of student achievement
provide evidence of current status of
student knowledge and understanding
• Learning is demonstrated by growth in
student achievement from one point in time
to a another point in time – not by status at
either point time alone
Uses of Growth Measures
• Informing students, parents, and teachers about
individual student progress
– Measuring individual student growth can be useful, but
utility is limited due to low reliability of individual
student gain scores
• School accountability systems
– Growth measures have substantial advantages over
status measures for accountability
– Unlike status measures, growth takes prior
achievement into account
Growth vs. Value Added
• Value-added models attempt to make
causal attributions
• Growth measures are purely descriptive
• In the absence of random assignment
causal attributions are always suspect and
subject to challenges (see, for example,
Raudenbush, 2004; Rubin, Stuart &
Zanutto, 2004)
Interpreting Growth Measures
Physical growth Achievement growth
• 9 year old boy grew 5 measure
inches in past year (is that • 4th grader grew 25 scale
a lot or a little?) score points since 3rd
grade (Is that a lot or a
little?
• Average 4th grade scale
• Relative interpretation is score is 21 points higher
easier than absolute than average 3rd grade
(Average height of 9 year score, the gain of 25
boys is 49 inches points is at the 65th
compared to 45 inches for percentile)
8 year old boys, the 5 inch
growth is at the 65th
percentile)
About this copy
Why Measure Growth — ETS, October 2009.
This is an image-based copy of the original PowerPoint slides; builds and animations are flattened.