Mid-Chapter Quiz
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A statistic is a measure that describes a characteristic of a sample. A parameter is a measure that describes a characteristic of a population.
Population: All children at a community pool
Sample: Random sample of 25 children
Example Statistic: The percent of children visiting the pool at least once a week by the random sample of 25 children
Example Parameter: The percent of children visiting the pool at least once a week among all the children at a community pool
A population consists of all the members of a group of interest. Since it may be impractical to examine every member of a population, a sample — a subset of the population — is sometimes selected to represent the population. The sample can then be analyzed to draw conclusions about the entire population.
Let's consider our situation.
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A random sample of 25 children at a community pool is asked if they visit the pool at least once each week. The percent responding yes is calculated. |
Here, the population consists of all children at a community pool. However, the sample consists of only 25 of them selected at random. Let's recall the definitions of a statistic and a parameter as well as their characteristics.
| Definition | Characteristics | |
|---|---|---|
| Statistic | A statistic is a measure that describes a characteristic of a sample. | A statistic can — and usually will — vary from sample to sample. |
| Parameter | A parameter is a measure that describes a characteristic of a population. | Parameters are fixed values that can be determined by the entire population, but are typically estimated based on the statistics of a carefully chosen random sample. A parameter will not change, for it represents the entire population. |
With the above definitions in mind, we can think of a possible statistic and a possible parameter.