Which sampling practice ensures variability over process cycles by collecting samples frequently?

• A. Take several increments and composite them to form the sample.
• B. If possible, mix the material before sampling.
• C. Collect the sample in a container made of material that will chemically react with the sample.
• D. Sample frequently enough to allow for the identification of process cycles.

Answer: (D)

Capturing variability across process cycles requires sampling often enough to reflect cycle changes rather than averaging them out. If you sample too infrequently, you might miss peaks, troughs, or shifts that occur during a cycle, making it hard to understand how the process behaves over time. Frequent sampling builds a record of how measurements rise and fall with each cycle, revealing true variability and any recurring patterns. The other practices either mask or contaminate variability: composing multiple increments into one sample smooths out cycle-to-cycle differences; mixing the material before sampling reduces heterogeneity and hides fluctuations; using a container that can react with the sample risks chemical changes and erroneous results. So, collecting samples at a frequency that tracks the cycles best demonstrates variability over time.