Samples and Populations

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3.5. Samples and Populations#

We want to accurately predict the probability of an event.

We use an accurate mathematical model that correlates the attributes of a sample with that of the population it was taken from.

What is a sample? What is a population?

Population#

A population, N, is the total number of observable objects.

Such as:

  • The total number of processors in a production run.

  • The human population of the earth.

  • The number of students enrolled at Portland Community College.

Tip

The number of values in a popluation is typically described by the capital letter N.

Populations usually contain a very large numbers of objects. It would be difficult to evaluate every case so a sample is taken.

Sample#

A sample, n, is any subset of the population.

Such as:

  • 1000 processors from a production run of 1 million.

  • The population of the United States is a sample of the population of the earth.

  • The number of students enrolled in a class, are a sample of the population of students enrolled at Portland Ccommunity College.

Tip

The number of values in a sample is typically described by the lowercase letter n.

Capitalization matters when describing the numbers of elements in a sample (n) or population (N).

Ideally, a sample should be representative of the population, and there are guidelines with relating the characteristics of a sample to that of its population.

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