Reconsidering the Measurement of Political Knowledge

Political knowledge has emerged as one of the central variablesin political behavior research, with numerous scholars devotingconsiderable effort to explaining variance in citizens' levelsof knowledge and to understanding the consequences of this variancefor representation. Although such substantive matters continueto receive exhaustive study, questions of measurement also warrantattention. I demonstrate that conventional measures of politicalknowledge—constructed by summing a respondent's correctanswers on a battery of factual items—are of uncertainvalidity. Rather than collapsing incorrect and "don't know"responses into a single absence-of-knowledge category, I introduceestimation procedures that allow these effects to vary. Grouped-datamultinomial logistic regression results demonstrate that incorrectanswers and don't knows perform dissimilarly, a finding thatsuggests deficiencies in the construct validity of conventionalknowledge measures. The likely cause of the problem is tracedto two sources: knowledge may not be discrete, meaning thata simple count of correct answers provides an imprecise measure;and, as demonstrated by the wealth of research conducted inthe field of educational testing and psychology since the 1930s,measurement procedures used in political science potentiallyresult in "knowledge" scales contaminated by systematic personalityeffects.