Bias or Fallacy?

All 24 scenarios, with answers

Each quiz draws twelve of these at random.

1. Priya has already decided the expensive blender is the one for her. She reads every five-star review, skims past the one-star complaints about leaking lids, and tells her partner the research is overwhelmingly positive.
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   Confirmation bias (bias). Confirmation bias is seeking and weighting evidence that fits what you already believe. Priya did look at evidence, but she gave the favourable reviews more weight and discounted the rest. Read the guide

2. A used-car dealer opens by saying the hatchback 'usually goes for $18,000'. Marcus had planned to offer around $12,000, but he ends up feeling clever for getting it down to $15,500.
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   Anchoring (bias). Anchoring is when estimates drift toward the first number you see. The dealer's opening figure pulled Marcus's sense of a fair price toward it. Read the guide

3. After a week of news coverage about a shark sighting, Leo refuses to swim at the beach. He happily drives two hours on the highway to get there.
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   Availability heuristic (bias). The availability heuristic is judging frequency by how easily examples come to mind. Dramatic, recent news is easy to recall without being common, so the rare risk feels bigger than the everyday one. Read the guide

4. A new neighbour is quiet, wears glasses and always carries a novel. Dana is sure he must be a librarian, never stopping to consider how many more salespeople than librarians live in her city.
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   Base-rate neglect (bias). Base-rate neglect is ignoring how common something is in favour of a vivid description. Dana judged by how well he matched a stereotype instead of asking how common each job is to begin with. Read the guide

5. Twenty minutes into a dull, overlong film, Sam wants to leave. His friend insists they stay to the end because the tickets cost $22 each.
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   Sunk cost fallacy (bias). The sunk cost fallacy is continuing because of what you have already spent. The money for the tickets is gone either way; only future costs and benefits should drive the decision. Read the guide

6. A podcast host says the secret to success is skipping college, pointing to three famous founders who dropped out. She never mentions the dropouts whose companies failed.
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   Survivorship bias (bias). Survivorship bias is drawing conclusions only from the cases that made it through a filter. The failures never appear in the sample, so the advice looks better than it is. Read the guide

7. The underdog team wins the championship. The next morning Jordan tells everyone at work it was obvious all season, although last month he had picked them to finish fourth.
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   Hindsight bias (bias). Hindsight bias is the 'I knew it all along' feeling once an outcome is known. People rate outcomes as more predictable after learning them and often fail to notice their judgment has shifted. Read the guide

8. Two supermarkets sell the same minced beef. One label says '80% lean' and the other says '20% fat'. Most shoppers in a store survey say the first one sounds healthier.
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   Framing effect (bias). The framing effect is making a different choice from the same facts depending on the wording. Restating the choice the other way round is the countermeasure. Read the guide

9. Nina tells her book club she'll repaint the spare room 'this Saturday'. She has said the same about the last three rooms she painted, each of which took most of a month.
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   Planning fallacy (bias). The planning fallacy is underestimating how long your own tasks will take. The fix is to use how long similar past projects really took. Read the guide

10. A driver swerves past Omar on the motorway. 'What a selfish jerk,' he mutters, without considering that the driver might be rushing someone to hospital.
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    Fundamental attribution error (bias). The fundamental attribution error is explaining others' behaviour by character rather than circumstances. Asking what situation would make you act the same way is the countermeasure. Read the guide

11. The hiring panel is impressed by a polished, charismatic candidate. Without checking her references or work samples, they agree she must also be organised and good with budgets.
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    Halo effect (bias). The halo effect is when one good trait colours judgments of unrelated traits. Scoring each criterion separately, before an overall rating, counters it. Read the guide

12. Ravi spent a weekend assembling a flat-pack desk that wobbles slightly. When a friend offers him a sturdier one for free, he refuses, insisting his is the better desk.
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    IKEA effect (bias). The IKEA effect is overvaluing things you helped build. Getting a neutral person to evaluate it is the countermeasure. Read the guide

13. At a council meeting, Ana proposes adding two bike lanes on Main Street. Another resident replies, 'So you want to ban cars from the whole town and wreck every business here?'
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    Straw man (fallacy). A straw man attacks a distorted version of the claim. Ana proposed bike lanes, not a ban on cars; the reply knocks down a caricature instead of her actual position. Read the guide

14. A software engineer posts a careful benchmark showing the new database is slower. A commenter replies, 'Why would anyone trust him? He can't even keep his own blog design up to date.'
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    Ad hominem (fallacy). An ad hominem attacks the person instead of the argument. The state of his blog design is irrelevant to whether the benchmark is valid. Read the guide

15. A teenager's dad warns him that energy drinks every day are bad for his sleep. The teen shoots back, 'You drink four coffees a day, so you can't tell me anything.'
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    Tu quoque (fallacy). Tu quoque ('you too') dismisses criticism because the critic is guilty of it. The dad's habit makes him inconsistent, not mistaken. Read the guide

16. The club treasurer announces, 'Either we double the membership fee or the club shuts down by summer.' She doesn't mention sponsorships, a fundraiser or trimming costs.
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    False dilemma (fallacy). A false dilemma presents too few options. The answer is to name a third option, or to show the options are not mutually exclusive. Read the guide

17. A manager refuses a request to work from home one Friday. 'If I let you do it once, soon nobody will come in, and then the office will close for good,' she says, offering no evidence for any step.
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    Slippery slope (fallacy). A slippery slope claims a small step leads to disaster without support. Its quality depends on how probable each link in the chain is, and here none is backed by evidence. Read the guide

18. Chen started wearing a copper bracelet on Monday, and by Friday his cold was gone. He now recommends the bracelet to anyone with a sniffle.
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    Post hoc (fallacy). Post hoc reasons that because B followed A, A caused B. Chen inferred causation from sequence alone; the check is to look for a third factor and a mechanism. Read the guide

19. An advert for a cholesterol supplement features a famous racing driver saying it's the best thing for your heart. The advert offers no other evidence.
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    Appeal to authority (fallacy). An appeal to authority goes wrong when it cites an authority who lacks relevant expertise. A racing driver is not an authority on heart health. Read the guide

20. Kai says no true gamer would ever play on easy mode. When a friend points out that a champion streamer plays story games on easy, Kai replies, 'Then he isn't a real gamer.'
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    No true Scotsman (fallacy). No true Scotsman redefines the category to dodge a counterexample. Kai changed the definition of 'gamer' only to avoid being refuted. Read the guide

21. A reporter asks the mayor why the bus service is running late so often. The mayor replies that the city next door has much worse potholes, and moves on to the next question.
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    Red herring (fallacy). A red herring introduces an irrelevant topic to divert attention. The neighbouring city's potholes have nothing to do with late buses. Read the guide

22. A shop assistant recommends a herbal sleep tonic. 'It's made entirely from plants, so there's no way it could be harmful,' she tells the customer.
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    Appeal to nature (fallacy). An appeal to nature assumes natural means good and artificial means bad. Being plant-based says nothing on its own about whether the tonic is safe. Read the guide

23. A coach signs the five highest-scoring players from five different clubs. 'Every one of them is a star,' he tells reporters, 'so this will obviously be a great team.'
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    Composition (fallacy). The fallacy of composition assumes that what's true of the parts is true of the whole. Star players do not automatically make a great team. Read the guide

24. In an online thread, Mia argues that seatbelts save lives but backs it up with a weak anecdote. Another user replies, 'That's just an anecdote, so seatbelts obviously don't help.'
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    Fallacy fallacy (fallacy). The fallacy fallacy concludes that a claim is false because the argument for it is bad. Someone can argue for a true claim badly. Read the guide