Ap Stats

Simple Random Sample (SRS)

Choosing individuals from the population so that every individual and group has an equal chance of being selected.

Systematic Random Sample

Choosing individuals from a population by selecting a random starting point and a fixed 'sampling interval.'

Cluster Sampling

Dividing the population into heterogeneous clusters and selecting a few at random to perform a census within them.

Stratified Random Sample

A sampling method that divides the population into strata and performs a separate SRS in each stratum.

Multi-stage Sample Design

A sampling strategy that combines multiple stages of different sampling methods.

Population

The entire group of individuals we want information about.

Census

Data collected about an entire population, making it so that everybody is 'sampled.'

Sampling Frame

A list of individuals from which a sample is chosen, ideally the entire population.

Sample

A part of the population that we examine in order to gain information.

Pilot

A trial run of a survey administered to a small sample to improve the survey before a larger sampling process.

Parameter

A value that tells you something about the population.

Statistic

A value that tells you something about a sample.

Statistical Inference

Making conclusions about the population based on the sample.

Bias

The design of a study that systematically favors certain outcomes.

Convenience Sample

Data collected from a conveniently available pool of respondents.

Voluntary Response Bias

Bias created by a sample composed of people that volunteer to participate.

Undercoverage

When some groups are left out of the sample selection process.

Nonresponse

When individuals chosen for the sample cannot be contacted or refuse to cooperate.

Response Bias

When the accuracy of responses is affected due to various factors.

Wording of Questions

Confusing or leading questions that can introduce bias.