Chapter 10

Population

Population

The entire group of individuals or instances about whom we hope to learn.

Sample

A subset of the population examined in order to gather data.

Sample Survey

A study that collects data from a sample to learn about the population from which the sample was drawn.

Bias

Any systematic error in a study that results in an incorrect estimate of the population parameter.

Randomization

The practice of using chance methods to assign subjects to treatments to eliminate bias.

Sample Size

The number of observations or individuals in a sample.

Census

A study that attempts to collect data from every individual in the population.

Population Parameter

A numerical value summarizing a characteristic for the entire population.

Statistic & Sample Statistic

A numerical value summarizing a characteristic for a sample.

Representative

A sample that accurately reflects the characteristics of the population.

Simple Random Sample (SRS)

A sampling method where every member of the population has an equal chance of being selected.

Sampling Frame

A list of individuals from whom the sample is drawn.

Sampling Variability

The natural variation in sample statistics from one sample to another.

Stratified Random Sample

A sampling method where the population is divided into strata, and random samples are taken from each stratum.

Cluster Sample

A sampling method where the population is divided into clusters, and entire clusters are randomly selected.

Multistage Sample

A sampling method that combines several sampling methods.

Systematic Sample

A sampling method where every nth individual is selected from a list or queue.

Pilot Study

A small trial run of a study to test its methods and procedures.

Voluntary Response Sample

A sample consisting of individuals who choose themselves by responding to a general invitation.

Voluntary Response Bias

Bias introduced when individuals can choose on their own whether to participate in the sample.

Convenience Sample

A sample chosen based on ease of access and not randomness.

Undercoverage

When some members of the population are inadequately represented in the sample.

Nonresponse Bias

Bias introduced when a significant portion of those sampled fails to respond.

Response Bias

Bias that occurs when the behavior of the respondent or interviewer influences the results.