The impact of misclassification due to survey response fatigue on estimation and identifiability of treatment effects

*Statistics in Medicine*(2011) 30:3560-3572.

**Abstract**

Response fatigue can cause measurement error and misclassification problems in survey research. Questions asked later in a long survey are often prone to more measurement error or misclassification. The response given is a function of both the true response and participant response fatigue. We investigate the identifiability of survey order effects and their impact on estimators of treatment effects. The focus is on fatigue that affects a given answer to a question rather than fatigue that causes non-response and missing data. We consider linear, Gamma, and logistic models of response that incorporate both the true underlying response and the effect of question order. For continuous data, survey order effects have no impact on study power under a Gamma model. However, under a linear model that allows for convergence of responses to a common mean, the impact of fatigue on power will depend on how fatigue affects both the rate of mean convergence and the variance of responses. For binary data and for less than a 50% chance of a positive response, order effects cause study power to increase under a linear probability (risk difference) model but decrease under a logistic model. The results suggest that measures designed to reduce survey order effects might have unintended consequences. We present a data example that demonstrates the problem of survey order effects. Copyright (C) 2011 John Wiley & Sons, Ltd.