Measurements of cognitive skill by survey mode: Marginal differences and scaling similarities

This paper addresses how measurements of cognitive skill differ based on survey mode, from a face-to-face interview to a self-completed survey, using the Wordsum vocabulary test found in the General Social Survey. The Wordsum acts as a proxy for general cognitive skill, and it has been used to predict a variety of political variables. Therefore, knowing differences in cognitive skill by mode are important for political science research because of the proliferation of self-completed Internet surveys. I leverage a large-scale mode experiment that randomizes a general population sample into a face-to-face or self-completed interview. Results show that historically easy questions are more likely to yield correct answers in the face-to-face treatment, but modest-to-difficult test questions have a higher rate of correct answers in the self-completed treatment (marginal distributions). A cognitive skill scale using item response theory, however, does not differ by mode because the ordering of ideal points does not change from a face-to-face interview to a self-completed survey. When applying the scale to a well-established model of party identification, I show no difference by mode, suggesting that a transition from face-to-face interviews to self-completed surveys may not alter conclusion drawn from models that use the Wordsum test.