Computerized adaptive testing
The common (Verbal and Quantitative) multiple-choice portions of the exam currently uses a section-based computer-adaptive testing (CAT) format that automatically changes the difficulty of the sections as the test taker proceeds with the exam, depending on the number of correct or incorrect answers that are given. Currently, the GRE revised General Test allows the test-taker to move forth and back, and change answers within a section, and thus the questions in a given section are not adaptive.
While questions within each section are not adaptive, performance on the first Verbal and Quantitative section influences the difficulty in the second section of the same topic. This approach to administration yields scores that are of similar accuracy while using approximately half as many items. However, this effect is moderated with the GRE because it has a fixed length; true CATs are variable length, where the test will stop itself once it has zeroed in on a candidate’s ability level.
The actual scoring of the test is done with item response theory (IRT). While CAT is associated with IRT, IRT is actually used to score non-CAT exams. The GRE subject tests, which are administered in the traditional paper-and-pencil format, use the same IRT scoring algorithm. The difference that CAT provides is that items are dynamically selected so that the test taker only sees items of appropriate difficulty. Besides the psychometric benefits, this has the added benefit of not wasting the examinee’s time by administering items that are far too hard or easy, which occurs in fixed-form testing.
An examinee can miss one or more questions on a multiple-choice section and still receive a perfect score of 170. Likewise, even if no question is answered correctly, 130 is the lowest possible score.