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 diners at the restaurant
Sample: Random sample of 15 diners
Example Statistic: Median of the money spent on each meal by the random sample of 15 people.
Example Parameter: Median of the money spent on each meal offered at the restaurant.
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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At a restaurant, a random sample of 15 diners is selected. The amount of money spent on each meal is recorded. |
Here, the population consists of all diners in the restaurant. However, the sample consists of only 15 diners randomly selected. 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.