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Field
Randomization Method
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Before
stratified randomization done in office by a computer
Households will be clustered by dividing their past summer and winter electricity consumption based on the median, classifying them into groups with consumption above or below the median for each season.
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After
Stratified randomization done in office by a computer (Households will be clustered by dividing their past summer and winter electricity consumption based on the median, classifying them into groups with consumption above or below the median for each season)
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Field
Power calculation: Minimum Detectable Effect Size for Main Outcomes
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Before
To design the current experiment, we referred to the results of a previous study that offered rebates and calculated the required sample size. We then considered the number of households we could realistically secure in the field and decided to assign 250 households to each group.
The previous study set a rebate of 100 yen per kWh and observed an average electricity reduction of 5%. Based on this result, achieving statistical significance at the 5% level with 250 households per group requires at least a 7.5% reduction. A 100 yen rebate is unlikely to generate such an effect. Therefore, we increased the rebate to 200 yen per kWh in order to promote a greater reduction in electricity usage and reach the targeted effect size.
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After
We determined that 10 groups, as described above, were necessary to achieve the objectives of this experiment. We then considered the number of households we could realistically recruit in the field and decided to assign 250 households to each group.
Our power calculation indicated that, with 250 households per group, detecting a statistically significant treatment effect at the 5% level would require at least a 7.5% reduction in electricity consumption.
In our previous study (Ida et al., 2023), we offered a rebate of 100 Japanese Yen per kWh and observed an average reduction in electricity usage of 5%. Since a 100 Yen rebate was unlikely to produce a reduction of 7.5% or more, we decided to increase the rebate to 200 Yen per kWh in order to reach the target effect size.
Ida, T., Ishihara, T., Ito, K., Kido, D., Kitagawa, T., Sakaguchi, S., & Sasaki, S. (2024). Choosing Who Chooses: Selection-Driven Targeting in Energy Rebate Programs. (No. w30469). National Bureau of Economic Research.
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