A new diagnostic instrument, the Conceptual Survey on Wave Optics (CSWO), was developed and validated on 224 high school students (aged 18-19 years) in Croatia. The process of test construction, which included the testing of 61 items on the total of 712 students is presented. The final version of the test consists of 26 multiple-choice items which…

Although content validity--how well each item of an instrument represents the construct being measured--is foundational in the development of an instrument, statistical validity is also important to the decisions that are made based on the instrument. The primary purpose of this study is to demonstrate how simulation studies can be used to assist…

This study examined the validity of test accommodation in third-eighth graders using differential item functioning (DIF) and mixture IRT models. Two data sets were used for these analyses. With the first data set (N = 51,591) we examined whether item type (i.e., story, explanation, straightforward) or item features were associated with item…

A comparison is presented of alternate-choice and true-false item forms used in an undergraduate natural science course. The alternate-choice item is a modified two-choice multiple-choice item in which the two responses are included within the question stem. This study (1) compared the difficulty level, discrimination level, reliability, and…