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Applying SGP to the STAR Assessments. Daniel Bolt Dept of Educational Psychology University of Wisconsin, Madison. Some Unique Features of STAR Assessments. Same CAT assessment is administered within and across years (possible to generate look-up tables for the calculation of SGP)
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Applying SGP to the STAR Assessments Daniel Bolt Dept of Educational Psychology University of Wisconsin, Madison
Some Unique Features of STAR Assessments • Same CAT assessment is administered within and across years (possible to generate look-up tables for the calculation of SGP) • Multiple STAR administrations to a student are possible throughout the year, and can occur at different times and/or frequencies for different students
Why SGP may be Useful with STAR Assessments • Different STAR scores may be associated with different amounts of measurement error (e.g., extremely low or high STAR scores are sometimes of questionable validity) • There often exists more/less variability in growth observed across students at different initial STAR score levels
Some Practical Issues Related to Administration of STAR Assessments • How frequently and at what intervals should STAR be administered to get reliable estimates of end-of-year scores? Does the answer depend on the initial (fall) score of a student? • Is there practical value in the use of SGP for answering this question (in contrast to alternative approaches, such as ordinary least squares---OLS--- regression methods)?
Goals of the Present Study • Examine SGP as a methodology for quantifying growth and for studying the precision of end-of-year growth predictions using STAR Assessments • Compare SGP against competing methodologies (OLS regression) in terms of their reported precision of end-of-year predictions
Sample Sizes (Students with Fall, Winter & Spring Assessments)
Evaluating the Precision ofSpring Score Predictions How well do winter assessments improve our predictions of end-of-year outcomes? Are the winter assessments more/less useful depending on the fall score obtained by the student? In answering these questions, we find it useful to examine changes in the confidence intervals for spring scores defined by the SGP percentile cuts
Comparison of SGP & OLS Intervals, Math Grade 1 According to SGP %ile cuts According to OLS Standard Error of Prediction
STAR Math, Grades 1-6 SGP OLS
STAR Math, Grades 7-12 SGP OLS
STAR Reading, Grades 1-6 OLS SGP
STAR Reading, Grades 7-12 OLS SGP
STAR Early Literacy, Grades K-4 OLS SGP
Adding Winter Scores as Covariates with SGP • Using 80% interval width curves as a baseline, we can further examine how much the intervals are reduced when adding a winter assessment • The decline in the 80% interval can be used as an indicator of the added precision provided by the winter assessment
STAR Math Example SGP OLS
STAR Math, Grade 1-6 SGP OLS
STAR Math, Grades 7-12 OLS SGP
STAR Reading Example SGP OLS
STAR Reading, Grades 1-6 OLS SGP
STAR Reading, Grades 7-12 OLS SGP
STAR Early Literacy Example SGP OLS
STAR Early Literacy, Grades K-4 OLS SGP
Evaluating Predicted Spring Scores in Terms of State Proficiency Thresholds • The accuracy of SGP and OLS predictions can also be compared against the thresholds associated with state-specific proficiency categories • By assuming normally distributed residuals (with constant variance) for OLS, SGP and OLS can each be used to define a probability that the spring score will exceed a predefined threshold
Example of SGP Percentile Cuts against State-Defined Proficiency Category Proficiency Threshold
Comparing SGP and OLS on Accuracy of Proficiency Predictions • aEstimated STAR cutscores for the Tennessee Comprehensive Assessment Program (TCAP) • bEfron’s Pseudo R2
Extending SGP to Accommodate Multiple Intermediate Assessments How can additional intermediate assessments be used in SGP to further improve predicted spring scores? Challenge: Handling varying-time point assessment schedules One possible solution: Linear interpolation to fixed node locations
Conclusions and Future Directions • Our SGP analyses suggest substantial variability in the precision of spring score predictions for STAR Math, Reading and Early Literacy depending on fall scores • There is clear value in incorporating winter assessments into SGP---the largest value occurs for students with extreme fall scores in STAR Math, intermediate fall scores in STAR Reading • More experimentation needed to determine how best to make use of multiple intermediate assessments within SGP