# Fundamentals of Statistics

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## 1.2 The Fourth and Fifth Words

After you know what you are analyzing, or, using the words of Section 1.1, after you have identified the variables from the population or sample under study, you can define the parameters and statistics that your analysis will determine.

### Parameter

CONCEPT A numerical measure that describes a variable (characteristic) of a population.

EXAMPLES The percentage of all registered voters who intend to vote in the next election, the percentage of all patients who are very satisfied with the care they received, the mean weight of all the cereal boxes produced at a factory on a particular day.

### Statistic

CONCEPT A numerical measure that describes a variable (characteristic) of a sample (part of a population).

EXAMPLES The percentage of registered voters in a sample who intend to vote in the next election, the percentage of patients in a sample who are very satisfied with the care they received, the mean weight of a sample of cereal boxes produced at a factory on a particular day.

INTERPRETATION Calculating statistics for a sample is the most common activity because collecting population data is impractical in most actual decision-making situations.