A Method to Evaluate Mode Effects on the Mean and Variance of a Continuous Variable in Mixed-Mode Surveys

Mixed-mode surveys, in which different respondents complete the survey by different modes, become increasingly popular. That said, such surveys may lead to a confounding of two forms of mode effects, i.e., selection effects and measurement effects. Exclusive focus on mixed-mode data almost precludes disentangling both effects. In this paper, we show how this problem can be circumvented merely by comparing mixed-mode data with a comparable single-mode sample. The proposed method allows estimating the mode effects on the mean and variance of a continuous variable. As an illustration, the authors estimate mode effects on six items on opinions about surveys.