Short answer. Item difficulty (denoted *p*) is the proportion of students who answered a given quiz question correctly. A question that 80% of students got right has *p* = 0.80. The metric is poorly named — *higher* difficulty value = *easier* question — but it's a foundational stat for evaluating quiz quality.
What the values mean
p = 1.0: Every student got it right. Either trivially easy, or a freebie. Not useful for distinguishing students.p = 0.80-0.90: Easy. Good for confidence-building, foundational checks.p = 0.50-0.70: Medium. Most useful for assessment — discriminates between students who know and don't know.p = 0.20-0.40: Hard. Good for stretch questions; use sparingly.p < 0.20: Either too hard for the cohort, or a broken question.p = 0: No one got it right. Almost certainly a broken question.How to use it
For a typical quiz:
Aim for an average difficulty of 0.5-0.7 across all itemsDon't have all easy items (p > 0.85) — the quiz doesn't differentiateDon't have all hard items (p < 0.4) — the quiz frustrates without measuringMix difficulty levels so the quiz has a discrimination curveItem difficulty + item discrimination
Item difficulty alone is incomplete. A question with p = 0.50 might be:
A great question (top half of class gets it right, bottom half doesn't) — high [item discrimination](/blog/what-is-item-discrimination)A coin-flip question (every student has 50/50 odds) — low item discriminationA *reverse-discrimination* broken question (bottom half gets it right, top half misses) — negative discriminationUse both metrics together. A good quiz has medium-difficulty items with positive discrimination.
Most LMSs and quiz platforms show item difficulty after each quiz administration:
Canvas, Blackboard, Moodle: quiz statistics pageSimpleQuizMaker: per-question analytics across all submissionsAfter every quiz, scan the difficulty distribution. The items with p > 0.95 (everyone right) and p < 0.15 (almost no one right) are usually the ones to review or rewrite.
Common mistakes
Confusing the name. Higher value = easier. Not intuitive. Many teachers reverse this in their heads.Ignoring difficulty data when grading. The "everyone missed Q5" pattern usually means Q5 is broken, not that everyone failed to learn.Treating low p as a teaching problem when it's a question problem. Verify the question is well-written before concluding students don't know the material.[What Is Item Discrimination?](/blog/what-is-item-discrimination)[How to Write Good Quiz Questions](/blog/how-to-write-good-quiz-questions)[How to Write Hard Quiz Questions](/blog/how-to-write-hard-quiz-questions)[Quiz Analytics — Teacher Guide](/blog/quiz-analytics-teacher-guide)Generate a quiz and see per-question difficulty after the first 5 submissions.
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