Volume 18, Issue 3 (1989)
Summarizing Trends in Student Achievement: A Comparison of Models
Mark R. Shinn, Roland H. Good III, Stephanie Stein
ABSTRACT: A substantial literature is evolving in support of direct, continuous monitoring of student academic achievement with data-based modifications of instruction.A critical element in proposed data-utilization strategies is an estimation of the slope of student skill acquisition. The split-middle (SM) and ordinary-least-squares(OLS) procedures have been recommended for this purpose, but little is known regarding their relative advantages. This study examined the accuracy and precision of the SM and OLS estimates of trend for 20 special education students whose reading progress was monitored for an academic year using Curriculum-Based Measurement (CBM) procedures. Although neither procedure resulted in systematic over- or under-predictions of performance, the OLS procedure regenerated estimates of future performance that were consistently closer to actual performance than the SM estimates. Thus, practitioners estimating the trend of CBM measures of reading skill can expect an increase in the precision of the estimates if they use an OLS estimate instead of the SM estimate.
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