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NEQC CONFERENCE THE 56TH NORTH EAST QUALITY CONFERENCE
 
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Sample Size Conundrum for Reliability Testing: How Big Or Small ?
Nihar Senapati,Lead Reliability Engineer
GE Healthcare
439 South Union Street 3rd Floor,Lawrence,MA 01843
Nihar.Senapati@ge.com


Reliability practitioners and design assurance engineers tend to confront a dilemma while selecting a sample size. In most cases the size of the sample is arbitrarily chosen convenient to the situation and availability of the sample test units. Limited understanding of the design assurance engineer or reliability test personnel on sample size estimation process dilutes the primary concept and spirit of reliability test process. Small sample size produces test results, which donít buy the approval from management decision makers. Confidence in such results is usually very low. On the other hand, a more than adequate sample size (though augurs well on the meaningfulness of test conclusions) tends to be cost and cycle time prohibitive. Sample size estimation process can be a challenge starting from a simple reliability demonstration test to conducting a Highly Accelerated Life Test (HALT).

The paper focuses on the several risk factors including producerís risk and consumerís risk and various cost factors while discussing an optimal sample size. This paper also discusses sample size with consideration to various apriori statistical failure distributions. The goal is to showcase several paths for sample size determination in the industrial environment and reduce errors in reliability testing.


Presenter:

Nihar Senapati Nihar Senapati is a Lead Reliability Engineer with GE Healthcare in Lawrence, MA. He works in hardware and software Reliability areas and holds a MS in Reliability and Quality engineering from University of Arizona, Tucson.

He is also a CRE, CQE and a Six Sigma Black Belt from ASQ. He has consulted and published many papers on various aspects of Reliability, Quality and Six sigma process improvement initiatives. Nihar is a member of ASQ and IEEE Boston Reliability Chapter.


 

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