Terminologies

Population

A population is a statistical universe. It is defined as a collection of existing attributes of some natural phenomenon or a collection of potential attributes when a process is involved. Populations can be either finite or infinite. A subset of population selected by some relevant criteria is called a subpopulation.

Sample

A sample is an observed part of a population. Selection of a sample is a rich methodology in itself, but, unless otherwise specified, it is assumed that the sample is selected at a random. The randomness ensures that the sample is representitive of its population.

Statistics

The term statistics has a plural form but is used in the singular when it relates to methodology. A sample summary is called a statistic. For example, a sample mean is a statistic, and sample mean and sample range are statistics. The ultimate summary for quantifying a population attribute is a statistical model.

Composite Sample

When a sample is large and many observations are repetitive, data are often recorded as group with their unique values and their frequencies. This is called a composite sample.

Experiment

A phenomenon, action, or procedure where the outcomes are uncertain.

Sample Space

Set of all possible outcomes in an experiment.

Event

A collection of outcomes; a subset of the sample space.