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Appendix B:
Deriving the Effectiveness Index
The Effectiveness Index (EI) is
derived by comparing actual scoreson standardized tests
with scores as predicted by a model whichfactors in
the role community characteristics play in educationaloutcomes.
The Community Effects Factor (CEF)
model was developed in a doctoral dissertation (Education
Achievement Communities: A New Modelfor "Kind of Community"
in Massachusetts Based on anAnalysis of Community Characteristics
Affecting Educational Outcomes, May 1999, University
of Massachusaetts,Amherst). That work is the basis for
determining school effectiveness. The model examines
the relationship between selected demographiccharacteristics
and educational outcomes. These characteristicsinclude:
average education level, average income, poverty rate,single-parent
status, language spoken, and percentage of school-agepopulation
enrolled in private schools. These variables werechosen
because they correlate with achievement and because
theeducation literature identifies them as connected
to academicperformance.
In order to refine a better CEF model,
it is first necessary tofactor the impact of these demographic
variables on each other. This can be done through a
technique known as principal componentanalysis that
is a statistical mechanism that reduces many variablesto
a few salient ones that have the most impact on an outcome.
Once the factors have been identified, a regression
analysisproduces the equations that can be used to either
build a kind-of-communitymodel or to predict expected
district performance on achievement tests. The degree
to which a community'scharacteristics lifts or lowers
test scores is reflected in aCommunity Effects Factor
(CEF). a measure of demography.
The CEF, which is a measure of the
demographic lift or drag ofeach community concerning
educational achievement, is a good pointof departure
for analyzing school and school district effectiveness.
The CEF identifies expected levels of performance based
on communitycharacteristics which, for better or worse,
are very powerfulindicators of educational achievement
in Massachusetts. In thisanalysis, Weston is the most
demographically advantaged communityin the state in
terms of educational outcomes (CEF = + 2.8),and Lawrence
is the least advantaged (CEF = - 4.8). The CEF has a
strong relationship, or correlation,to test scores.
Correlation is a process that identifies
the interdependence ofone variable with another. Correlation
simply shows "the extentto which two things typically
run together." [The Economist, 6 Dec. 1997, p. 82].
Correlation is not equivalent to causation;it can only
reveal tendencies between variables, not identifycauses.
Correlations simply demonstrate relationships. A perfectcorrelation
would be 1.0. For example, the correlation betweeninches
and feet is 1.0 because it is a perfect linear fit;
12inches always equals one foot. Correlations in real
world situationsinvolving human behavior are never 1.0.
The correlation, or the connection,
between spending (Per-PupilExpenditure or PPE) and achievement
in Massachusetts is .28, whichis relatively low. While
spending clearly matters, merely increasingspending
levels has a relatively weak impact on results. Increasingly,many
people are coming to the realization that how a system
spendsmoney is more important than how much money it
spends. The achievementoutcome accounted for by the
community effects factor (CEF) ismuch stronger; that
relationship is .86. This is not to say thecommunity
context, the CEF, is the most important determinantof
school success, but it is a significant element that
must bea major consideration in any plan to improve
education in disadvantagedareas.
The Effectiveness Index was generated
in the following manner:
- Utilize the 1998 MCAS results as an outcome indicator
forachievement in each of the state's most populous
200 communities. (NOTE: Thismodel does not evaluate
results in the 151 smallest communities of the statewhich
comprise about 7% of the population.)
- Utilize the CEF model to predict a score for each
district. This predicted score is based solely on
community characteristic asthey affect educational
outcomes.
- Compare the actual to the predicted score. Systems
whoseactual scores are significantly higher than predicted
scores and whose absolutescores are at or above state
average are identified as effective. systems with
positive effectiveness indexes but scores belowstate
average are identified as noteworthy.
The basis for this model was developed
as a doctoral dissertation. The following provides detail
on the statistics behind the modelwhich is used to predict
expected scores based on demographics.
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