3. Collecting Data
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A bias is an error that results in a misrepresentation of a whole population.
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Every tenth employee who arrives at a company health fair answers a survey that asks for opinions about new health-related programs. Here, the population consists of all employees and the sample of every tenth employee surveyed. Let's recall how samples can be classified.
| Name | Characteristic |
|---|---|
| Random Sample | Each member of the population has an equal chance of being selected. |
| Self-selected Sample | Members volunteer to be included in the sample. |
| Systematic Sample | Members are selected according to a specified interval from a random starting point. |
| Stratified Sample | The population is first divided into smaller groups that share a similar characteristic. Members are then randomly selected from each group. |
| Cluster Sample | The population is first divided into groups called clusters. All of the members in one or more of the clusters are selected. |
| Convenience Sample | Members that are readily available or easy to reach are selected. |
Every tenth employee who arrives at a company health fair answers a survey. Therefore, this is systematic sample. Note that only employees who attend the company health fair are surveyed, however. These employees are more likely to have strong opinions about the new health-related programs. Therefore, we could conclude that the sample is biased.