Back to History

Fields Changed

Registration

Field Before After
Last Published May 14, 2018 10:39 AM May 15, 2018 11:19 AM
Sample size (or number of clusters) by treatment arms At least 300 homeowners per treatment. Exact sample size per treatment will be determined after a pilot with 100 observations in the Voluntary treatment. At least 300 homeowners per treatment. Exact sample size per treatment will be determined after a pilot with 100 observations in the Voluntary treatment. --- The pilot results showed that about 25% of homeowners in the Voluntary treatments self selects into Insurance. No major changes were made in the design after the pilot results. We aim for at least 150 homeowners self selected into Voluntary Insurance and Voluntary Insurance Discount. For the premium discount versus Mandatory Insurance we expect a larger effect size. Therefore we will sample: 300 No Insurance 300 Baseline 200 Premium Discount 600 Voluntary 600 Voluntary Discount ----------------------------- 2000 in total (or more if budget allows)
Power calculation: Minimum Detectable Effect Size for Main Outcomes A sample size analysis assuming an alpha of 0.05 and a power of 80% indicated that we need a sample size of at least 252 participants per treatment in order to detect the smallest effect size* found in the scenario of a previous lab experiment, closest to our current parameters, with a Wilcoxon Mann Whitney test. * Mean investments in ECU in previous experiment No Insurance versus Mandatory Insurance: 2711.9 (sd 4102.4) versus 1793.4 (sd 3976.8): effect size 27% A sample size analysis assuming an alpha of 0.05 and a power of 80% indicated that we need a sample size of at least 252 participants per treatment in order to detect the smallest effect size* found in the scenario of a previous lab experiment, closest to our current parameters, with a Wilcoxon Mann Whitney test. * Mean investments in ECU in previous experiment No Insurance versus Mandatory Insurance: 2711.9 (sd 4102.4) versus 1793.4 (sd 3976.8): effect size 27% -> sample size needed 252 * Mean investments in ECU in previous experiment Mandatory Insurance versus Premium Discount: 1793.4 (sd 3976.8) versus 3550 (sd4560.1): effect size 41% -> sample size needed 78
Back to top