Technical Manual - Renaissance Learning

Reliability and Measurement PrecisionTest-Retest ReliabilityThe correlation of students’ scores on their first and second tests provides ameasure of the reliability of STAR Early Literacy tests that have been adaptivelyadministered.Over 9,000 students took part in the retest Reliability Study. Checks were made forvalid test data on both test administrations and to remove cases of apparentmotivational discrepancies. Figure 2 shows a scatterplot of 9,146 students’ scoreson initial test and retest. As the figure indicates, the correlation was 0.86 overall.Figure 2:Scatterplot of STAR Early Literacy Initial and Retest Scaled Scoresfrom the Validation Study (N = 9,146 Students; Correlation = 0.86)Table 13 lists the detailed results of the split-half, retest and generic reliabilityanalyses of STAR Early Literacy Scaled Scores on versions prior to the Enterpriseversion, both overall and broken out by grade. Given the ways in which STAR EarlyLiteracy will be used, the split-half reliability coefficient from the overall samplemay be the most appropriate one for evaluating the psychometric characteristicsof STAR Early Literacy as a measurement instrument. However, because there willbe some interest in STAR Early Literacy’s reliability at the school grade level, thetable also includes grade-by-grade reliability data.STAR Early LiteracyTechnical Manual48