Sampling Methods and Measures of Center & Variance

Population

Entire group being studied or surveyed.

Census

Survey of the entire population.

Sample

Subset of the population surveyed.

Biased Sample

Sample that may not represent the population.

Random Sample

Sample where each member has an equal chance.

Simple Random Sample

Members chosen randomly with equal likelihood.

Systematic Sample

Members selected using a systematic pattern.

Stratified Sample

Population divided into groups, then sampled.

Cluster Sample

Population divided into groups; all members surveyed.

Convenience Sample

Members chosen for easy accessibility.

Self-Selected Sample

Members volunteer to participate in the study.

Probability Sample

Each member has a nonzero chance of selection.

Margin of Error

Range where population percent likely lies.

Statistic

Number describing a sample's characteristics.

Parameter

Number describing a population's characteristics.

Data Consistency

Low variance indicates data is close together.

Data Variance

High variance indicates data is spread out.