Why AI gets it wrong: where hallucinations come from and how to catch them

1. 1

   One extra line in the notice

   Suppose a reading-group notice adds “Admission is free.” Our notes say nothing about admission. We cannot establish that it is false, but we also cannot support it. The defensible finding is: “Not established by this source.”

   

   This is an editorial example, not a quotation from a tested model. “Hallucination” commonly describes generated material that is false or unsupported by the supplied context. Different errors still need different checks.

   A changed date calls for source comparison, arithmetic needs recalculation and an outdated rule needs a date check. Identify the error and examine any conclusions that depend on it.

   Training, reasoning, retrieval, calculation tools and validation can reduce mistakes. No short instruction guarantees their elimination. Nor is it useful to claim models cannot calculate at all or that every limitation is permanent. Focus on checking the result in front of you.

1. 2

   Mark the kind of mismatch

   Put the source and draft side by side. In our invented exercise the reference details are 7 November, 2 p.m., second floor and one book. The table shows four useful checks for this notice, not an exhaustive error taxonomy.

   Omissions matter. “Meet at the library” may be true but insufficient for a newcomer because the floor is missing. Label “free” as unsupported rather than deciding without evidence that it is false.

   Write a precise finding such as “no support for free admission” or “second floor omitted.” It becomes a checkable revision request. A complete rewrite may change facts you have already verified.

   Editorial examples of notice errors

   Source or requirement	Draft issue	Check
   7 November	Changed to 9 November	Restore the supplied date
   Second floor	Floor omitted	Add the floor
   No price supplied	Says admission is free	Remove or flag
   For a first-time attendee	Uses unexplained internal shorthand	Explain in plain language

2. 3

   Check arithmetic by recalculating

   For a made-up inventory exercise, suppose each of 627 boxes contains 483 items. Calculate 483 × 627. Splitting it gives 289,800 + 13,041 = 302,841. Check with a calculator or spreadsheet.

   Compare that with the deliberately incorrect editorial example 303,141: a difference of 300. A detailed explanation and correct unit labels cannot rescue a wrong total. The incorrect number is not a reported model response.

   Even correct arithmetic can use the wrong assumptions. Empty boxes or unequal quantities would make this multiplication unsuitable. Check the meaning of the data, the formula and then the answer.

   Real prices, taxes and exchange rates require applicable, current inputs. A tool processes a formula; it does not establish that the assumptions fit the situation. Our invented inventory is not evidence for a real transaction.

3. 4

   Look for support, not just a link

   Open the cited page, locate the supporting passage and check its date and scope. A real link to last month’s library notice may not support today’s opening hours.

   Keep the claim beside its supporting passage and the date you checked it. An official document might concern a different branch or a future plan. Confirm what the document actually covers.

   If you cannot open or read the source, record that limitation. A title or search snippet does not mean you read the full text. Seek an accessible primary source or omit the unresolved claim.

   Two assistants agreeing is not the same as two independent sources. Comparing answers can expose disagreements worth investigating, but agreement alone does not verify a claim.

4. 5

   Give unknowns a visible place

   When supplying material, specify how unknowns should be handled: “Use only facts established in the notes; list missing details separately.” That provides a review criterion, not a guarantee that every unsupported claim will be caught.

   A confirmation list is a useful output. For our notice it includes admission and registration. Keep established details clear while distinguishing what remains unknown.

   “I am certain” and a confidence score do not add evidence. Without a validated measurement method, do not read such scores as objective accuracy. Ask which passage supports the claim.

This is a learning check, not a test you must pass. Use the explanations to understand the ideas.

1. Q1The notes omit admission but the draft says it is free. Mark it false, true or unsupported by this material, and choose the next action.

   Write your thoughts (optional)

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   Read the answer and explanation

   Unsupported by this material. The notes establish neither free nor paid admission. Remove or flag the claim and obtain confirmation if publication requires it.

   I read and understood the explanation

   This is your own review, not an automatic score.

2. Q2With the practice quantities of 483 items per box and 627 boxes, a draft total is 303,141. Give the correct total, the difference and one assumption to check first.

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   Read the answer and explanation

   The correct total is 302,841; the draft is 300 too high. Check whether every box actually contains 483 items. These are invented practice quantities, and correct arithmetic does not validate the assumption.

   I read and understood the explanation

   This is your own review, not an automatic score.

3. Q3A source link opens, but it gives last year’s opening hours for a different library branch. What must you check instead?

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   Read the answer and explanation

   Find the applicable branch’s current notice and its effective dates. A working link alone is not supporting evidence. If you cannot find an applicable source, record the hours as unconfirmed.

   I read and understood the explanation

   This is your own review, not an automatic score.

1. 6

   Try it: a three-line review record

   Compare your notice with the original notes and connect each event detail. Record each mismatch in three fields: problem, evidence and revision. For example: “Free admission / absent from notes / remove and add to organizer-confirmation list.”

   

   Read the corrected notice again. Verify the fix and ensure it did not change other details. Finish after the necessary checks, not after an arbitrary time limit.

   The method scales, but longer or higher-impact work requires more checking and sometimes specialist judgment. Record unresolved questions and who can answer them. Start with a small piece of material you understand and complete the whole review.