To estimate the ICC, we fitted unconditional two-level models (students-within teachers/classrooms) separately for the PPS posttest, PPS delayed posttest, and GMADE posttest.
Tables 3-5 present the multilevel results for the PPS posttest, PPS delayed posttest, and GMADE posttest outcomes.
For the GMADE posttest, Table 5 shows that SBI was a significant predictor, with an SBI-versus-control difference of 0.32 SD, or 63% of SBI students scored above the mean of control students.
Preliminary analyses of the PPS posttest, PPS delayed posted, and GMADE posttest outcomes separately produced ICCs of .18, .19, and .19, respectively (all p < .001).
Treatment was not a significant predictor for the GMADE posttest in Table 5, but once again pretest and math achievement level were significant predictors.
Contrary to findings in prior SBI studies (Jitendra et al., 2009; Jitendra et al., 2011; Jitendra et al., 2013; Jitendra et al., 2015), we found that SBI outperformed the control condition on the GMADE assessment (g = 0.32) even though only one third of the GMADE items reflect concepts taught in the study.
(in press) study, there was no effect on the GMADE; however, the ES of g = 0.26 is non-negligible (see What Works Clearinghouse, 2014), and the lack of statistical significance may be attributable to the modest number of classrooms.
This is an important finding in that we found positive effects on the GMADE that contrast with the findings of Jitendra et al.
Results from Table 3 show statistically significant differences in the posttest total scores between the treatment group and both control groups, after adjusting for the preintervention GMADE Total Test scores.
Eta-squared, or percent variance explained, of .12 and .13 indicated large effect size (Cohen, 1988), demonstrating that students who received the at-home numeracy intervention made substantial gains on their posttest scores on the GMADE Total Test score.
The researchers found a statistically significant and large effect of the at-home numeracy intervention on the GMADE Total Test score for students included in the study.