Items / Reference templates / BP002
REF-BP002-1
C01 conditional probability · C01.2 conditional from two way table · target easy, CD2 · split val · reference items carry their template's native demand and difficulty
Pending
A table from a clinic record review records 202 patients. Of the 123 who are over 60, 89 report side effects; of the 79 who are under 60, 41 report side effects. A patient is chosen at random from among the over 60. What is the probability that this patient reports side effects?
Explanation (as written by the item's author)
Conditioning on over 60 restricts the sample space to those 123 patients, of whom 89 report side effects, so the probability is 89/123 = 0.724.
| Option | Code | Catalogue meaning | Author's rationale |
|---|---|---|---|
| A | M-JOINT-AS-COND | Uses the joint probability P(A and B) where the conditional P(A|B) was required. | 89/202: the joint probability, dividing by the whole sample. |
| B (key) | KEY | 89/123: the conditioning group is the over 60 row. | |
| C | M-INV-COND | Inverts the conditional: reports P(B|A) when P(A|B) was asked (confusion of the inverse). | 89/130: conditions on the wrong margin, giving P(over 60 | report side effects). |
| D | M-WRONG-DENOM | Divides by the full sample size rather than by the size of the conditioning group. | 130/202: the marginal probability of report side effects, ignoring the conditioning. |
Quality flags · 0 fired
- duplicate options (integrity) not firedTwo options are identical after normalisation.
- numerically equal options (integrity) not firedTwo options denote the same number (e.g. 0.5 and 1/2 and 50%).
- missing options (integrity) not firedFewer than four non-empty options.
- key out of range (integrity) not firedThe keyed answer is a probability outside [0, 1] (or a percentage > 100).
- all none of above (cue) not firedAn option is 'all/none of the above' or 'both A and B'.
- key uniquely longest (cue) not firedThe key is the longest option by at least 20% (length cue).
- key uniquely shortest (cue) not firedThe key is the shortest option by at least 20%.
- distractor out of range (cue) not firedA distractor is a probability outside [0, 1]; it can be eliminated without the construct.
- absolute terms in distractors (cue) not firedDistractors (only) use absolute terms such as always/never/must/proves, a known cue that they are wrong.
- stem option overlap cue (cue) not firedThe key alone repeats a content word from the stem.
- grammatical mismatch (cue) not firedThe stem ends in 'a'/'an' and some options do not agree with it.
- key is hedged only (cue) not firedOnly the key contains hedging language (may/might/plausibly/likely).
- numeric middle key (info) not firedOptions are numeric and the key is one of the two middle values. Informational; tested at set level against the 0.5 chance rate.
- negative stem (style) not firedStem uses NOT/EXCEPT/LEAST phrasing.
- overlong stem (style) not firedStem exceeds 110 words.
- inconsistent numeric format (style) not firedNumeric options mix fractions, decimals and percentages, or use differing decimal precision.
- unit mismatch (style) not firedOptions carry different units.
- option length imbalance (style) not firedLongest option is more than 2.5x the shortest.
- rationale value mismatch (metadata) not firedA distractor's stated rationale computes a value ('= x') that is not the option it is attached to: the distractor does not actually execute the misconception it claims.
Validator output
PoT not yet run for this item.
Answering probes
Probes not yet run for this item.
Shortcut results
| Heuristic | P(key) |
|---|---|
| longest option | 0.25 |
| shortest option | 0.25 |
| convergence | 0.25 |
| stem overlap | 0.25 |
| numeric middle | 0.00 |
| hedged option | 0.25 |
| position prior | 0.00 |
Provenance and generation trace
- Method
- reference_template / —
- Model
- none
- Source
- parameterised template T-C01.2-table, written by the AssessAI build agent (Claude); no external item bank; not human-reviewed
- Prompt hash
—- LLM calls · cost
- 0 · $0.00000 · 0.0 s
- Parser notes
- none