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Section 1

Descriptive Statistics

A population is the group to be studied, and population data is a collection of all elements in the population. For example:

  • All the fish in Long Lake.
  • All the lakes in the Adirondack Park.
  • All the grizzly bears in Yellowstone National Park.

A sample is a subset of data drawn from the population of interest. For example:

  • 100 fish randomly sampled from Long Lake.
  • 25 lakes randomly selected from the Adirondack Park.
  • 60 grizzly bears with a home range in Yellowstone National Park.
  • Populations are characterized by descriptive measures called parameters. Inferences about parameters are based on sample statistics. For example, the population mean (µ) is estimated by the sample mean (). The population variance (σ2) is estimated by the sample variance (s2).