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Quality control of sampling: proof of concept
Michael Thompson1, Barry J Coles, Joseph K Douglas
1School of Biological and Chemical Sciences, Birkbeck College (University of London), UK.
The Analyst
|February 6, 2002
Summary
This study introduces a practical quality control method for composite sampling. It uses random allocation of sample increments into two composites, enabling precise assessment of sampling variability without extra resources.
Area of Science:
- Environmental science
- Analytical chemistry
- Statistical process control
Background:
- Effective quality control (QC) is crucial in sampling procedures.
- Composite sampling, where multiple sample increments form a single composite sample, is common.
- Assessing the precision of composite sampling is essential for reliable data.
Purpose of the Study:
- To present a practical and resource-efficient method for quality control in composite sampling procedures.
- To enable the assessment of sampling precision independent of analytical precision.
Main Methods:
- The proposed method involves randomly allocating sample increments into two equal-sized, smaller composite samples.
- Each of the two half-sized composite samples is analyzed separately.
- The absolute difference between the results of the two analyses is plotted on a one-sided control chart, similar to a Shewhart chart.
Main Results:
- The control chart effectively monitors the precision of the sampling process.
- In scenarios where analytical precision is negligible, the chart exclusively reflects sampling precision.
- The method is practicable and requires no additional sampling resources or time.
Conclusions:
- The developed method provides a robust approach to quality control in composite sampling.
- It allows for the direct assessment of sampling precision, which is vital for data integrity.
- This technique is efficient, requiring no extra resources beyond standard sampling and analysis procedures.