Exercise 13 Page 614

Recall how samples can be classified.

Error: It is a self-selected sample.
Correction:

Practice makes perfect

We are looking for an error in identifying the type of sample that is used.

Let's first 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.

Notice that we use only the surveys that are returned. There is no systematic rule used to select members for the population since households in the neighborhood decide whether or not they return the survey. Therefore, this is a self-selected sample. We are ready to correct the mistake.

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