Unit 8 · Detecting Reasoning Errors
Faisal's Piano Chance — Necessary Condition Chain
Lesson 6 of 10
About this lesson
Faisal tells Sajid the minimum practice needed to have "any chance" of passing. Sajid practises more than that minimum, then concludes he's certain to pass. The mistake sounds reasonable — he's doing MORE than the minimum! — but it's one of the most important logical errors in OC TS: confusing "I need this to have a chance" with "this guarantees I'll succeed." These two ideas are completely different.
Chapters
Question
Faisal says: “To have any chance of passing your piano exam, you will need to practise for at least 15 minutes, four times a week.”
Sajid says: “I practise every day for twenty minutes or more, so I’m sure to pass the exam.”
Which one of these sentences shows the mistake Sajid has made?
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