Increasing Precision without Altering Treatment Effects: Repeated Measures Designs in Survey Experiments

The use of survey experiments has surged in political science. most common design is the between-subjects which outcome only measured posttreatment. This relies heavily on recruiting a large number subjects to precisely estimate treatment effects. Alternative designs that involve repeated measurements dependent variable promise greater precision, but they are rarely used out fears these will yield different results than standard (e.g., due consistency pressures). Across six studies, we assess this conventional wisdom by testing experimental against each other. Contrary fears, measures tend same as more while substantially increasing precision. These also offer new insights into effect size and heterogeneity. We conclude encouraging researchers adopt providing guidelines for when how them.