Sampling bias is the error caused by assuming that a sample is representative of the whole population when it is not.
It is the error that says “Everything else like this must be similar to what I’m looking at” without a good foundation (empirical or logical) for doing so.
You might survey the Netherlands in intricate detail and rule out the possibility of the Himalayas.
You might catch and examine a thousand fish from shallow water and never imagine what deep-sea species are like.
You might make a million observations of water above 0°c and never guess the properties of ice.
You might think:
- “The rest of this country must be like the <1% of it I’ve seen.”
- “I caught lots of waves today – surfing is easy.”
- “All people like this must behave in this (objectionable/endearing) way.”
- “People are mostly smart, like my friends.”
- “People are mostly dumb, like the idiots who around me.”
- “I have never seen this problem solved, so it must be impossible.”
- “We do this all the time, so it must be easy for everyone.”
- “I’m rich / poor.”
- “My 2 kids turned out okay / struggled in life, so I’m a good / bad parent.”
- “I’m great at tennis – the best in my village.”
- “That ended well / badly so it was a good / bad decision.”
- “The world is a nice / horrible place.”
- “This is how service is done everywhere.”
- “I am a high / low achiever.”
- “This small amount of pollution I’m making doesn’t matter.”
- “I’m a good / generous / bad / selfish person.”
- “Treating people like this is normal.”
See also: