Before calculating standard deviation or plotting a control chart, SM recommends making at least how many determinations on a sample?

Before calculating standard deviation or plotting a control chart, SM recommends making at least how many determinations on a sample?

• A. False
• B. True
• C. Not recommended
• D. Not applicable

Answer: (B)

Before calculating a standard deviation or plotting a control chart, you need enough data from a sample to reveal true variability rather than just a single measurement. Making at least a few determinations per sample provides a reliable estimate of dispersion and a meaningful basis for control limits. With multiple replicates, random measurement error is averaged out, so the standard deviation and the chart reflect the process rather than a fluke in one reading. That’s why the statement is considered correct: replication is a standard practice to ensure meaningful statistical results. In practice, labs often aim for three to five determinations per sample, though the exact minimum can depend on the method and guidance. The other options imply replication isn’t needed or relevant, which contradict how these tools are used in quality control.

Before calculating a standard deviation or plotting a control chart, you need enough data from a sample to reveal true variability rather than just a single measurement. Making at least a few determinations per sample provides a reliable estimate of dispersion and a meaningful basis for control limits. With multiple replicates, random measurement error is averaged out, so the standard deviation and the chart reflect the process rather than a fluke in one reading. That’s why the statement is considered correct: replication is a standard practice to ensure meaningful statistical results. In practice, labs often aim for three to five determinations per sample, though the exact minimum can depend on the method and guidance. The other options imply replication isn’t needed or relevant, which contradict how these tools are used in quality control.