There are some important terms that we should be familiar with before we get too deeply into the subject of statistics. These are listed below. It is also highly recommended that you read the section entitled Some Key Terms in Chapter 1 of the text or another resource to get a more in-depth explanation of these concepts.
Population |
Definition:
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The entire collection of persons, things, or objects we want to study.
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Examples: |
cows, pigs, horses, jaguars, rabbits, squirrels |
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Sample |
Definition:
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A portion of the population which represents that population (the sample will have the same characteristics as the entire population).
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Examples: |
horses, jaguars, squirrels |
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Parameter |
Definition:
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A number that is a property of the population.
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Examples: |
- average GPA (Grade Point Average)
- proportion of voters in a district
- standard deviation of house prices
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Statistic |
Definition:
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A number that is a property of the sample. In most cases, the parameter is not known. It is estimated by the statistic.
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Examples: |
- average GPA = 3.25
- proportion of voters in a district = 13/22
- standard deviation of house prices = $10,000
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Variable |
Definition:
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Denoted by capital letters like X and Y. It is a characteristic of interest of the population.
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Examples: |
 Let X = the number of continents in the world that a person has visited
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Data |
Definition:
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Actual values of the variable.
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Examples: |
2 Continents (Asia & Europe) |
