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effect[3]. Blind measurements when operators do not know that an assessment is conducted could result in different (higher) variability.

Inclusion of precision statements is required by all ASTM test methods, and this recommendation is based on the Eisenhart[1] study. Unfortunately, some standards related to the measurement of filtration efficiency, including ASHRAE and ISO standards, do not include the precision statements. These statements could have a significant impact on publication of test results, comparison and filter selection decision process.

Dr. Thad Ptak has over 30 years of experience in filtration technologies, aerosol science and indoor air quality. He has conducted extensive research in the areas of development of filter media and filters, portable air cleaners, indoor air quality, sensors for IAQ and instrumentation for particle generation and measurement.

References

1. C. Eisenhart, Realistic Evaluation of the Precision and Accuracy of Instrument Calibration Systems, J. Res. Natl. Bur. Stand. 67C, 1963

2. ASTM E 1488, Standard Guide for Statistical Procedures to Use in Developing and Applying Test Methods

3. R. Gillespie, A History of the Hawthorne Experiments, Cambridge University Press, 1991

We

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