Technical Manual - Renaissance Learning

Reliability and Measurement PrecisionTest-Retest Reliabilityadministered, using only the items that were retained in the STAR Early Literacyitem bank following the Calibration Study.Retest reliability data from both studies are reported in the following sections.Calibration Study DataAs mentioned earlier, the Calibration Study included a test-retest Reliability Study,in which selected students took calibration tests twice. The two tests wereadministered on different days, and each student took a different form on retest tominimize repetition of the same items. The correlation of students’ scores on theirfirst and second tests provides one measure of the reliability of STAR Early Literacytests.Over 14,000 students took part in the retest Reliability Study. Figure 1 shows ascatterplot of students’ scores on initial test and retest. As the figure indicates, thecorrelation was substantial: 0.87 overall.Figure 1:Scatterplot of STAR Early Literacy Initial and Retest Scaled Scoresfrom the Calibration Study (N = 14,252 Students; Correlation = 0.87)Validation Study DataAs in the Calibration Study, some students participating in the Validation Studytook STAR Early Literacy on two occasions, separated by a few days. The itemsadministered to a student during the initial test were not repeated during thesecond test.STAR Early LiteracyTechnical Manual47