Sample
Sample is the subset of a population that a researcher actually collects and analyses. Because observing an entire population is usually too costly, the sample is used to estimate unknown population characteristics.
See it move
A four-step flow moves from Population — where the true mean μ is unknown and the size N is large — through a Random draw in which each unit carries a known selection probability, then to a Sample of n observed and recorded values, and finally to Inference, where the sample mean x̄ and variance s² serve as estimates of the unknown population parameters μ and σ². The connectors label the transitions: selecting from the population, collecting measurements, and computing statistics that carry the uncertainty of the original draw into the estimates.
Check yourself
A researcher wants to understand study habits of all first-year business students across Europe. She surveys only the 80 students in her own university's programme. Which statement best identifies the problem with her approach?