Test Analysis
Distractor Efficiency Calculator
Measure how many incorrect options attract at least the chosen minimum response count.
Enter the distractor review
Retain option-level evidence
Store each option's response count, response share, point-biserial or group pattern when available, and content review decision.
If options are randomized, verify that position-level exports were mapped back to the actual option text.
Omitted responses do not identify a distractor and should remain separate from option selections.
After revising an option, treat the new wording as a new item version for longitudinal comparison.
Define whether a distractor selected by the minimum share in the full group must also show a sensible performance-group pattern. A popular option chosen mainly by high performers may signal ambiguity rather than effective misconception targeting.
For multiple-response items, selections are not mutually exclusive and this simple option count needs adaptation.
Keep response counts after excluding invalid attempts so the functional threshold uses the same denominator as the rest of the item analysis.
After revising distractors, pilot the entire option set again. Replacing one weak option can change how respondents perceive the stem and remaining choices, so historical selection shares should not be assigned to the new version. Store version-specific option text with every analysis.
Classify every incorrect option
- State the functional threshold.
- Exclude the keyed option.
- Classify each distractor once.
- Review nonfunctioning and suspiciously popular options.
The threshold belongs in the report
One analyst may require 5% selection while another uses a fixed count or additional discrimination evidence.
The same response pattern can therefore receive different classifications.
Three distractors under review
Two of three distractors meet the chosen criterion, giving 66.7% efficiency. Thirty-two of 100 responses are incorrect.
Common planning questions
What selection threshold should be used?
Choose and disclose a standard appropriate to the assessment program.
Is an unused distractor always bad?
It may be implausible, but small samples and strong mastery can also produce low selection.
Can a distractor be too attractive?
Yes. Review for ambiguity or a key problem.
The equation used here
Scope: A distractor is functional only under the analyst's stated selection threshold and review rule.
Popularity alone is insufficient
A frequently chosen distractor may reveal a misconception, misleading wording, or more than one defensible answer.
Inspect option content and group patterns before revising it.
Option analysis can be paired with tools that place option behavior beside the item's facility, compare performance groups on the item, or compare assessment evidence with completion of a learning workflow.