The multiple-choice science exercises used by the National Assessment of Educational Progress include an "I Don't Know" (IDK) alternative to estimate more accurately knowledge of groups of respondents. Group percentages of IDK responses were examined and compared with correct responses to see if the IDK introduces bias. Variance common…

Across the field of educational assessment the case has been made for alternatives to the multiple-choice item type. Most of the alternative types of items require a subjective evaluation by a rater. The reliability of this subjective rating is a key component of these types of alternative items. In this paper, measures of reliability are…