Exam Negative Marking Guess Threshold Calculator

Method and input definitions

Expected points per attempt = p × correct points − (1 − p) × wrong-answer penalty. Setting expected points to zero gives the break-even accuracy p = penalty ÷ (correct points + penalty).

Worked example

For +4 points correct and a 1-point wrong-answer penalty, the break-even accuracy is 1 ÷ (4 + 1) = 20%. At exactly 20%, expected score is zero before any blank score.

Assumptions and limits

The formula assumes one fixed correct reward, one fixed wrong penalty, and a blank response worth zero. It does not account for partial credit, uncertainty in a student's probability estimate, or test policy.

Inputs are bounded to finite values shown in the form. Displayed results are rounded for readability (probability percentages and proportion fractions to four, other measures to two decimal places); whole-count outputs remain exact. A changed field clears a prior result so an outdated estimate is not presented as current.

References and related tools

These are direct calculations over user-supplied values; no external empirical benchmark is assumed.

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