Citizens' political knowledge has always been believed as an important dimension of the quality of democracy. A citizenry that possesses basic knowledge of political affairs is helpful for the development of democracy. Although many political scientists have theoretically explored the origins and determinants of political knowledge, as well as empirically developed a number of measurement techniques to gauge the level of citizens’ political knowledge and in turn analyze its relationship with other concepts, at present the evidence for the effectiveness of these techniques is still lacking. That is, from a methodological perspective, discussion about the reliability and validity of political knowledge measures is rare, let alone an analysis of whether the degree of difficulty of questionnaire items that were created by using a composite measurement method is sufficient in distinguishing citizens with different levels of political knowledge. In fact, whether in the end these composite measurement items should be considered as an index or a scale currently draws little scholarly interest. The study's objective is to examine the validity of political knowledge items found in the 2012 TEDS, and to verify whether or not the questions, in addition of possessing the form of an index, also fit the special structure of a Guttman scale. The study has obtained the following research findings. First, TEDS has seven questions that cover different aspects of political knowledge, but there seems to be too many measures focusing on political figures. Second, level of political knowledge is found to have a statistically significant and consistent relationship with individual background variables which founded in past research, thus indicating that the measurement validity is satisfactory. Third, although the seven questions’ degrees of difficulty are within the range (between 0.1 and 0.9) set by convention, there remains room for improvement in the difficulty levels between questions. Fourth, the survey questionnaire items measuring political knowledge fit the logical structure of a Guttman scale, and are cumulative in nature. Last, from standpoint of scale construction, items measuring political knowledge can be simplified further, although future surveys may also consider designing - and incorporating - questions of appropriate difficulty level that are related to the role of government, policy accomplishments, or political environment, thereby increasing the item discrimination power of the political knowledge scale.
