No. 263 · Evidence · Fallacy
Hasty Generalisation
A few examples, however vivid, are not enough to support a sweeping rule.
In the Almanac
“Gall’s bumps”, 1790s–1800s · “Target Canada”, 2013–2015
Both stories in full, three ways to use it and where it misleads.
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Questions
What is Hasty Generalisation?
A Hasty Generalization turns a handful of cases into a broad rule. Phrenology grew from a few hand-picked skull observations, and Target bet its US success would carry over when it opened 124 Canadian stores in 2013.
How do you avoid Hasty Generalisation?
Before acting on a pattern, ask how many cases you really have and whether they are representative. Test small before scaling up, and hold early conclusions loosely until more evidence arrives.
When does Hasty Generalisation matter?
Hasty Generalisation is one of the 68 mental models for evidence, the situations where you ask: Is this really true? Within that, it belongs to “When research goes wrong”, alongside Anecdotal Evidence, Data Dredging and Non-Response Bias.
What is an example of Hasty Generalisation?
Two stories show it at work: Gall’s bumps (1790s–1800s) and Target Canada (2013–2015). Both are told in full in The Mental Models Daily Almanac, which has two stories for each of its 365 models.
Which mental models are related to Hasty Generalisation?
Law of Large Numbers, Tendency to Stereotype and Inductive Reasoning. Hasty Generalisation itself comes from fallacy.