Predicting Rights-Only Score Distributions from Data Collected Under Formula Score Instructions.

Under a formula score instruction (FSI), test takers omit items. If students are encouraged to answer every item (under a rights-only scoring instruction, ROI), the score distribution will be different. In this paper, we formulate a simple statistical model to predict the score ROI distribution using the FSI data. Estimation error is also provided. In addition, a preliminary investigation of the probability of guessing correctly on omitted items and its sensitivity is presented in the paper. Based on the data used in this paper, the probability of guessing correctly may be close or slightly greater than the chance score.