Sampling: When is it used?

1. Sampling is used any time data is to be gathered.
Data cannot be collected until the sample size (how much) and sample frequency (how often) have been determined.

2. Sampling should be periodically reviewed.
When data is being collected on a regular basis to monitor a system or process, the frequency and size of the sample should be reviewed periodically to ensure that it is still appropriate.

The above article is an excerpt from the "Sampling" chapter of Practical Tools for Continuous Improvement Volume 1 Statistical Tools. The full chapter provides more details on setting sample size and frequency. This reference book is available from PQ Systems.