Evidence-Based Practices in Online Learning: A Meta-Analysis and Review of Online Learning Studies (2009). A systematic search of the research literature from 1996 through July 2008 identified more than a thousand empirical studies of online learning. Analysts screened these studies to find those that (a) contrasted an online to a face-to-face condition, (b) measured student learning outcomes, (c) used a rigorous research design, and (d) provided adequate information to calculate an effect size. As a result of this screening, 51 independent effects were identified that could be subjected to meta-analysis. Key findings include:
- Students who took all or part of their class online performed better, on average, than those taking the same course through traditional face-to-face instruction. Learning outcomes for students who engaged in online learning exceeded those of students receiving face-to-face instruction, with an average effect size of +0.24 favoring online conditions. The mean difference between online and face-to-face conditions across the 51 contrasts is statistically significant at the p < .01 level.
- Instruction combining online and face-to-face elements had a larger advantage relative to purely face-to-face instruction than did purely online instruction. The mean effect size in studies comparing blended with face-to-face instruction was +0.35, p < .001. This effect size is larger than that for studies comparing purely online and purely face-to-face conditions, which had an average effect size of +0.14, p < .05.
- Few rigorous research studies of the effectiveness of online learning for K–12 students have been published. The systematic search of the research literature found just five experimental or controlled quasi-experimental studies comparing the learning effects of online versus face-to-face instruction for K-12 students. As such, caution is required in generalizing to the K-12 population because the results are for the most part based on studies in other settings (e.g., medical training, higher education).