This week, we have a follow-on article from Chris Ryan, Manhattan GMAT’s Director of Instructor and Product Development. Chris introduced the concept of layering to us in this article on Sentence Correction. Layering is a technique used by a test writer to make a question more difficult. Today, Chris is going to show us how layering works in data sufficiency questions.

Note: I’ve repeated the introduction from the first article below, in case some of you haven’t read that one. If you did read the first one, the first few paragraphs will be review for you.

We all know that the GMAT is a computer adaptive test, and computer adaptive tests give us questions based on the difficulty level that we earn as we take the test. How do the test writers at ACT (the organization that writes the GMAT) determine which questions are harder than others?

First, ACT engages in a process called “normalization,” wherein all freshly written questions are tested by actual test takers to determine what percentage answer the questions correctly (we know these questions as experimental questions). If too many people answer correctly, the question may need to be toughened up. If too few people answer correctly, the question may need to be dumbed down. ACT is looking to assemble a pool of questions that covers a range of difficulty, from cakewalk to mind-bending, and the test takers help them do so.

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