Glossary term
Sample
The smaller group you actually measure, drawn from the larger group you want to learn about.
Visual intuition
n=4
n=16
n=64
Bigger samples make the estimate wobble less
Each dot is one spoonful's estimate of the whole pot: fair samples scatter around the truth, and bigger spoonfuls scatter less.
Example
To estimate the height of 10,000 students, you might measure a random sample of 200 of them and use that sample's average as the estimate.
How It Works
You taste a spoonful, not the whole pot. A sample works the same way: measure 1,000 voters instead of 50 million, and if the spoonful is drawn fairly — randomly, so everyone had an equal — it tracks the whole surprisingly well. The catch is how it is drawn: a poll answered only by landline owners is a stirred pot tasted from one corner.
Lessons
The Sample You See Matters
Your conclusion can be wrong when the data you see excludes important missing cases.
Small Samples Are Noisy
A small sample can land far from the truth by luck alone, while a larger one averages that luck away. This lesson shows how spread shrinks with the square root of the sample size and why the smallest groups dominate the extremes of any ranking.
Related Facts
Data Tricks
4 min · medium
The smallest towns top both the best and worst lists
Rank places by any rate — cancer, test scores, crime — and the extremes are dominated by the smallest places, because small samples swing far from the true rate by luck alone.
Data Tricks
4 min · easy
The missing planes mattered most
If you reinforce only the bullet holes on returning planes, you may protect the wrong places.