Political Analysis, 8:1 Reconsidering the Measurement of Political Knowledge

Political knowledge has emerged as one of the central variables in political behavior re-search, with numerous scholars devoting considerable effort to explaining variance in citizens ’ levels of knowledge and to understanding the consequences of this variance for representation. Although such substantive matters continue to receive exhaustive study, questions of measurement also warrant attention. I demonstrate that conventional mea-sures of political knowledge—constructed by summing a respondent’s correct answers on a battery of factual items—are of uncertain validity. Rather than collapsing incorrect and “don’t know ” responses into a single absence-of-knowledge category, I introduce es-timation procedures that allow these effects to vary. Grouped-data multinomial logistic regression results demonstrate that incorrect answers and don’t knows perform dissimi-larly, a finding that suggests deficiencies in the construct validity of conventional knowledge measures. The likely cause of the problem is traced to two sources: knowledge may not be discrete, meaning that a simple count of correct answers provides an imprecise measure; and, as demonstrated by the wealth of research conducted in the field of educational test-ing and psychology since the 1930s, measurement procedures used in political science potentially result in “knowledge ” scales contaminated by systematic personality effects.