A (representative) subset of a population, examined in hope of learning about the population.
A study that asks questions of a sample drawn from some population in the hope of learning something about the entire population.
The best defense against bias. Each individual is given a fair, random chance of selection.
The number of individuals in a sample. Determines how well the sample represents the population, not the fraction of the population sampled.
A numerically valued attribute of a model for a population. We rarely expect to know the true value, but we do hope to estimate if from sampled data.
Values calculated for sampled data. Those that correspond to, and thus estimate, a population parameter, are of particular interest.
A sample is said to be this if the statistics computed from it accurately reflect the corresponding parameters.
The natural tendency of randomly drawn samples to differ, one from another. Sometimes results in Sampling Error.
Stratified Random Sample
A sample design in which the population is divided into several subpopulations, or strata, and random samples are then drawn from each stratum.
Voluntary Response Bias
Bias introduced to a sample when individuals can choose on their own whether to participate in the sample.
A sampling scheme that biases the sample in a way that gives a part of the population less representation than it has in the population.
Bias introduced to a sample when a large fraction of those sampled fails to respond.