Acceptable Measurement Error in Psychology 1 Running head: Acceptable Measurement Error in Psychology Acceptable Measurement Error in Psychology

We derive standards for acceptable measurement error when inferring treatment effects from sample means. The standards arise from the amount of measurement accuracy required for sample means to beat a näıve benchmark estimator that randomizes the direction and magnitude of treatment effects. We show that at sample and effect sizes common to many areas of psychology, particularly in human subjects research, measurement error is too substantial to make meaningful claims about treatment effects. Alternatively, given some amount of measurement error, we provide minimum sample size recommendations for conducting meaningful experiments.