A Sampling Methodology for INSURV Material Inspections

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Naval Postgraduate School

This technical report summarizes research into sampling methods that the U.S. Navy Board of Inspection and Survey (INSURV) could employ during Material Inspections (MIs) of ships and submarines. The goal is to improve the Board’s efficiency in conducting MIs without compromising either Board effectiveness or inspection rigor.

The idea of sampling is that, rather than inspecting every item of a specific type—for example, portable CO2 bottles—onboard a ship or submarine, INSURV will only inspect a sample of those items. From the sample, INSURV would then characterize the ship’s or submarine’s entire complement of that item.

This report outlines a sampling methodology that is statistically rigorous and therefore quantitatively defensible, and it is implementable. It is based on well-known sampling methods, such as those described in Cochran (1977) and Lohr (1999).

The method described herein allows INSURV to specify the desired margin of error of the results on each item. It is expected that this decision will be based on the mission essentiality and/or safety criticality of each item, where items that are mission essential or safety critical will be given very small margins of error. Similarly, items that are not mission essential or safety critical will be given appropriately larger margins of error.