The Single-Best-Answer Workshop

Learning goals

Explain why the MBE uses single-best-answer format and what it demands of the author.
Write items where exactly one option is best — not merely one option that is true.
Convert "two defensible answers" drafts into clean single-key items.

Lesson 1 — Best, Not Merely True

The MBE's format is single-best-answer: several options may contain true statements of law, but only one answers the call. "Congress has broad power under the Commerce Clause" can be perfectly true and still wrong — if the call asks about the state's action. Your job is to make the key the best answer to this question, and to make each distractor fail on the question asked, not on general truth.

Lesson 2 — The "True But Unresponsive" Distractor

The most MBE-authentic distractor is the true statement that doesn't answer the call. It rewards examinees who match keywords instead of reasoning. When you write one, check that the key genuinely outperforms it on the call — not just in general correctness. If a solver can defend the distractor as answering the question asked, you don't have a distractor; you have a second key.

Lesson 3 — Calls That Force A Single Best Answer

Vague calls ("Which of the following is correct?") invite multiple true options. Focused calls ("Is the contract enforceable, and why?") let true-but-unresponsive distractors fail cleanly. The call is what makes single-best-answer possible — write it to decide the item, not to decorate it.

Lesson 4 — The Two-Key Rescue

When cold solvers split between two options, don't just pick one and ship. Diagnose: is one option more responsive to the call? Then sharpen the call to reward it. Are they responsive to different readings of ambiguous facts? Then disambiguate the facts. Is one simply wrong on a technicality? Then either fix the technicality or drop the option. A rescued item is stronger than the draft; a shipped two-key item is a flaw.

Spot-the-flaw drill

(intended key: A)

Fact pattern: Congress passes a statute regulating bakery working hours; findings say bakery conditions substantially affect the national baked-goods market. A bakery owner challenges the statute. Which best describes the constitutional analysis?

A. The statute is constitutional under the Commerce Clause B. Congress may regulate activities that substantially affect interstate commerce C. The Tenth Amendment reserves undelegated powers to the states D. Bakery working conditions are purely local matters

Flaw: options A and B are both true statements, and B is arguably the *better* doctrin

options A and B are both true statements, and B is arguably the better doctrinal statement — the item has two defensible keys because the call doesn't force a choice between a conclusion and its reasoning.

Correction

The call must ask for the holding applied to these facts, and the options must be parallel holdings-with-reasons. B's bare doctrinal statement becomes a distractor only when paired with a wrong application.

Model rewrite

— cold-solve verified: 2/2 (solvers chose A, A)

Fact pattern: (same). Is the statute constitutional?

A. Yes, because Congress may regulate intrastate economic activity that substantially affects interstate commerce B. No, because bakeries operating purely intrastate are beyond the commerce power C. No, because labor conditions are reserved to the states by the Tenth Amendment D. Yes, because the Necessary and Proper Clause gives Congress a general police power

Key: A

Drill key

The focused call ("is the statute constitutional?") plus parallel holdings-with-reasons makes A uniquely best. B/C/D each capture a genuine error. Both solvers chose A.

Sources

Haladyna, T. M., Downing, S. M., & Rodriguez, M. C. (2002). A review of multiple-choice item-writing guidelines for classroom assessment. Applied Measurement in Education, 15(3), 309–334.
National Conference of Bar Examiners. MBE Subject Matter Outline. (On the single-best-answer format and its scoring.)