Growth in Student Achievement:
Issues of Measurement, Longitudinal
Analyses & Accountability
Damian W. Betebenner
NCIEA
CCSSO NCSA, June 23, 2010
Discussions of student growth
lie at the intersection of three topics
Longitudinal Data Analysis/Applied Statistics
Overview
Accountability/Education Policy/Data Use
Measurement/Psychometrics
Measurement/Psychometrics
Examining student growth requires multiple
measurements of the same individual
Growth in what?
Overview
How much growth? (How is scaling involved
in answering this question?)
Is it enough growth?
Longitudinal Data Analysis/Applied Statistics
Many methods for analysis of longitudinal data
What are the relevant questions?
Are the analytic techniques capable of
Overview
answering those questions?
Does the data possess properties sufficient
for the analytic techniques employed? (e.g.,
vertical scale)
Does the analysis sustain the inferences
made from the data?
Accountability/Education Policy/Data Use
Education Policy & Accountability have many
goals and purposes
Why growth in accountability?
Overview
What are the goals and purposes of
accountability?
What is the theory of action behind
accountability?
How can we judge the validity of the
accountability system?
What about the current policy context?
Measurement/Psychometric Issues
Technical Considerations
Growth in what?
How much growth?
Scales for measuring growth
Ordinal (within-year, across year)
Interval (within-year, across year)
Vertical
Growth magnitude versus growth norm
Is it enough growth? Norm- versus criterion-
referencing (intersection of Accountability and
Measurement)
Growth in what?
Technical Considerations
Beneath any notion of change (i.e., growth)
is a construct that is changing over time
Height and weight are common points of
reference
Constructs in education are “slippery”
Need, at a minimum, an underlying
semantical referent (e.g. reading or math)
How much growth?
Technical Considerations
Are growth magnitudes possible in
education?
If calculable, are they interpretable absent
some norm?
Approaches to growth magnitudes:
Performance standards
Vertical scale with interval properties
Learning progressions (qualitative growth)
How much growth?
Technical Considerations
Performance Standards
Strengths Limitations
Anchors reference Few levels, mask
points for discussions substantial range within
about performance levels thus masking
student growth within
Growth is embedded level
in accountability metric Vary greatly in
stringency from state to
state so that “proficient”
performance lacks
meaning
How much growth?
Technical Considerations
Scale Scores
Strengths Limitations
Semi-continuous scores Difficult to interpret or
(many score points) explain to users
Can be used to create Vertical scales are hard
vertical scales across to defend
grade levels Claims of interval
Give the appearance of measurement
interval scales needed properties don’t hold to
by some analytical close scrutiny
models
How much growth?
Technical Considerations
Vertical Scale
Vertical & Interval scales required for some analytic
techniques:
Gain score calculation (magnitude of growth)
Growth curve analysis (rate of growth) (e.g., Willett &
Singer, 2003)
Vertical & Interval scales required for some questions:
Matthew effects: Do higher achievers grow faster than
lower achievers?
Growth rates relative to student age: Do students grow
more in later grades than earlier grades?
How much growth?
Technical Considerations
Vertical Scale
Vertical and/or Interval scales NOT required for some
analytic techniques:
Value-Added analyses: Most require interval, but not
vertical, scale. See Ballou (2008), Briggs & Betebenner
Auto-regressive analyses, growth norms
Vertical and/or Interval scales NOT required for some
questions:
Is a student’s progress (ab)normal?
Is a student’s growth sufficient to put them on track to
reach/maintain proficiency?
See Yen (2007) for an excellent list of questions
How much growth?
Technical Considerations
Magnitudes versus Norms
Physical growth Two Growth Quantities
9 year old boy grew 5 inches
in past year Magnitude of growth
Average increase in height
for boys between years 8 Relative amount of growth
and 9 is 4 inches
How much growth?
Achievement growth
4th grader grew 25 scale People expect an answer
score points since 3rd grade of magnitude
Average 4th grade scale
People need magnitude
score is 21 points higher
than average 3rd grade score embedded within a norm
How much growth?
Technical Considerations
Growth norms
Although normative comparisons are spurned
by criterion-referenced and standards-based
measurement advocates, norms can provide
a useful interpretive framework, especially in
the interpretation of student growth
“Scratch a criterion and you find a norm”
W. H. Angoff (1974)
Longitudinal Data Analysis Issues
Technical Considerations
Many Questions
Technical Considerations
How much annual growth did this (these) student(s)
make in reading?
Is (Are) this (these) student(s) making sufficient
growth to reach/maintain desired achievement
targets? (Growth-to-standard & Growth Model Pilot
Program)
Are students in particular subgroups (e.g., minority
students) making as much progress as other
students?
How much did this teacher/school contribute to
students’ growth over the last year? (Value-Added)
Again, see Yen (2007) for an excellent list of
questions
Many Techniques
Technical Considerations
Numerous data analysis techniques for use with
longitudinal data:
Gain scores (suitable scale required)
Cross-tabulation based upon prior and current
categorical achievement level attainment (e.g.,
value-tables, transition matrices)
Regression based approaches: growth-curve
analysis (HLM), fixed/mixed-effects models,
growth norms
Questions 1st, Analyses 2nd
Technical Considerations
Different growth analysis techniques often
address different questions
Different questions lead to different
conversations which lead to different uses
and outcomes
“It is better to have an approximate answer to the right
question than a precise answer to the wrong
question.”
J. W. Tukey
Model Purpose
Technical Considerations
Three general uses associated with statistical models (Berk, 2004):
Description: An account of the data. Model is true to the extent that it is
useful. Model quality judged by craftsmanship (de Leeuw, 2004)
Inference: Sample to Population. Model is true to the extent that the
assumed chance process reflects reality (super-population fallacy)
Causality: A causes B to happen. Model is true to the extent that plausible
causal theory exists and design criteria are met
Models are rarely descriptive despite minimal requirements
Inference and causality require information external to the data. Can’t
be validated solely from data
Models are often causal in nature but rarely meet rigorous criteria
necessary for such inferences
Value-Added Models
Technical Considerations
Causality
Value-Added Models (e.g., EVAAS) are a frequently
discussed type of growth model
Value-Added Models attempt to quantify the portion
of student progress attributable, usually to a teacher
or school
Value-Added is about the inferences made and not
the actual model
Causal attributions make value-added models well
suited for accountability discussions
In the absence of random assignment causal
attributions are always suspect and subject to
challenges (see, for example, Raudenbush, 2004;
Rubin, Stuart & Zanutto, 2004)
Value-Added Models
Technical Considerations
Causality
Value-added models return norm-referenced
effectiveness quantities
With regard to schools, quantities indicate whether a
school is significantly more or less effective than the
mean school effectiveness in the district or state
In a standards based assessment environment, how
much effectiveness is enough?
Especially important in light of universal proficiency
policy mandates
Growth-to-standard models created to provide
criterion-referenced growth models
Growth Model Pilot Program
Technical Considerations
Growth-to-standard
In response to requests for growth model use as part
of AYP, USED allowed states to apply to use growth
models
Fifteen states had models accepted
Models required to adhere to the “bright line
principle” of universal proficiency (growth-to-
standard)
Yen (2009) provides an excellent overview of the
models
Growth-to-standard models returned, in general,
results that closely aligned with AYP status results.
Growth versus Value-Added Models
Technical Considerations
Description & Causality
Growth measures are descriptive
Accountability has skewed discussions of
growth from description toward responsibility
(i.e., causality)
All measures (even VAM) are potentially
descriptive. However, some measures are
specially crafted for causal
inference/attribution
Good descriptive measures are interpretable,
informative and capable of multiple uses
Growth versus Value-Added Models
Technical Considerations
Description: Colorado Growth Model
The Colorado Growth Model uses student
growth percentiles to quantify student growth
Percentiles are familiar to stakeholders
Separating description from responsibility
has led to broad public acceptance including
teacher’s unions
Asking what schools or teachers are
associated with students demonstrating the
highest growth percentiles moves from
description toward value-added
Growth versus Value-Added Models
Technical Considerations
Description: Colorado Growth Model
Analysis employs quantile regression to calculate
conditional quantile relationships between current and
prior achievement
Student growth percentiles can also be criterion
referenced to accommodate growth-to-standard
This approach formed the basis of Colorado’s
successful application as part of the Growth Model Pilot
Program
Student growth percentiles provide a bridge connecting
value-added and criterion-referenced interests
Validating Models
Technical Considerations
There is no “gold standard” against which to
judge value-added or growth model results
Statistical model specification goes only part
way toward validation
Results should have credibility (i.e. face validity)
Because of their importance in accountability,
utility is a primary component of model validity
“All models are wrong but some are useful.”
G. E. P. Box
Accountability/Policy/Data Use
Technical Considerations
Accountability Systems
Technical Considerations
Purpose and requirements
Intended to improve education
Increase student achievement
Reduce achievement gaps
Increase efficiencies
Externally mandated and designed to hold
educators responsible for student learning
Impose sanctions and rewards based upon
results from large scale assessment
outcomes
Accountability and Growth
Technical Considerations
What type of growth?
Value-added provides a norm-referenced lens
judging growth/effectiveness against district/state
averages.
Growth-to-standard provides a criterion-referenced
lens judging growth toward community endorsed
achievement goals
Inferences about education quality based upon
value-added make judgments relative to students
reaching statistical expectation
Inferences about education quality based upon
growth-to-standard make judgments relative to
students reaching criterion-referenced destinations
Accountability and Growth
Technical Considerations
What type of growth?
States currently employ a variety of growth models
in service of accountability
Current policy mandates like NCLB are criterion-
referenced---establishing achievement
targets/destinations for all students
Need BOTH norm- and criterion-referenced growth to
reconcile individual focused policies like NCLB with
imperatives to judge education quality at the group
level (e.g., teacher or school)
Accountability Systems
Technical Considerations
Theory of action
Theory of action connects interpretations,
uses, and consequences (Gong, 2008)
Details connecting punishments/rewards
and outcomes are usually vague/incomplete
It is exactly these details that are critical to
validating the theory of action associated with
the accountability system’s use of growth any
growth/value-added metric
Accountability System Validity
Technical Considerations
Systemic Validity
“Assessment practices and systems of
accountability are systemically valid if they
generate useful information and constructive
responses that support one or more policy
goals (Access, Quality, Equity, Efficiency)
within an education system, without causing
undue deterioration with respect to other
goals.”
H. Braun (2008)
Descriptive Accountability
Technical Considerations
Building in systemic validity
“Accountability system results can have value without
making causal inferences about school quality, solely
from the results of student achievement measures and
demographic characteristics. Treating the results as
descriptive information and for identification of schools
that require more intensive investigation of
organizational and instructional process characteristics
are potentially of considerable value. Rather than using
the results of the accountability system as the sole
determiner of sanctions for schools, they could be used
to flag schools that need more intensive investigation to
reach sound conclusions about needed improvements
or judgments about quality.”
R. L. Linn (2008)
Descriptive Accountability
Technical Considerations
Part of a broader research program
Helpful in spotting provocative associations
A part of advocacy/informative discussions
(e.g, growth-gaps by ethnicity)
Informs policy goals and initiatives
The descriptive growth norms of the Colorado
Growth Model are an example of this type of
accountability metric
Bibliography
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Growth in Student Achievement: Issues of Measurement, Longitudinal Analyses & Accountability — CCSSO, June 23, 2010.
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