Fig 1.
Overview of the simulated experiments.
For each experiment, a sample of student scores were generated, and students were determined to have access or not to the textbook. Students were then randomly assigned to either an OER or Non-OER condition. The effect of access was simulated by reducing scores for students determined to not have access, but only in the Non-OER condition. Lastly, a statistical test the OER and Non-OER conditions was performed. See text for more information.
Fig 2.
Probability of successfully detecting an effect of OER as a function of access rate and sample size.
A study sample’s access rate to textbooks prior to adopting OER can severely hinder the likelihood of detecting an effect of OER, even at large sample sizes.
Table 1.
Estimated power of prior efficacy studies across different access rates (a).