StATS: What is a parameter?

A parameter is a number computed from a population. Contrast this with the definition of a statistic. A parameter is a constant, unchanging value. There is no random variation in a parameter. If the size of the population is large (as is typically the case), then you may find that a parameter is difficult or even impossible to compute. An example of a parameter would be:

• the average length of stay in the birth hospital for all infants born in the United States.

This page was written by Steve Simon while working at Children's Mercy Hospital. Although I do not hold the copyright for this material, I am reproducing it here as a service, as it is no longer available on the Children's Mercy Hospital website. Need more information? I have a page with general help resources. You can also browse for pages similar to this one at Category: Definitions, Category: Hypothesis testing.