Would you consider adding an "I don't know" option for student responses?

The way the system is designed to work, students receive credit only for those questions they answer correctly. All of the measures were scaled under the assumption of three possible answer choices, and no opportunity for students to select a " I do not know" answer.  We did originally consider the option of allowing students to indicate that they did not have enough information to answer a question, but ultimately opted to go with the standard forced response approach, as it has more empirical support in terms of providing technically adequate CBM assessments.

Often, students are able to eliminate one of the answer choices, as one is always written to be a far distractor. At that point, they are left with trying to select the most correct answer from two possible answer choices. Although sometimes, undoubtedly, students may close their eyes and guess, our research suggests that the scores provide robust information about student knowledge or lack thereof.