sample

A sample is (often) a much smaller, (generally) randomly collected subgroup of a larger population

Sampling Methods

• Simple Random Sample (SRS)
• Stratified Sample

Biased Samples

Biased samples are not representative of the population

Voluntary Response Sample -> ppl with strong opinions

Convenience Sample -> non-random way selected

Sampling Bias -> undercoverage , sampling frame

Non-response Bias -> can’t be surveyed

Response Bias -> response may have errors