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Sequential Reliability Testing

This tool provides the ability to plan a sequential reliability demonstration test for verification of equipment mean time between failure (MTBF), assuming an exponential failure distribution. Input parameters include the following:

See reference 1, chapter 24, for a more detailed discussion on sequential reliability testing and this blog post for an example. The Operating Characteristic (OC) curve is generated using Equation 7 in Reference 5.

Calculation Inputs:

1. Lower test MTBF (θ1, hours):
2. Nominal decision risks (α & β)
3. Discrimination ratio (d)

4. Chart overlay options:

4A. Comma separated value failure times, measured in cumulative unit-hours (accounting for time accumulated on all test units from test start).

4B. True MTBF (hours): Number of tests:

Featured Reference:

Reliability Theory and Practice
Reliability Theory and Practice

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  1. Bazovsky, Igor, Reliability Theory and Practice.
  2. Wald, A., Sequential Analysis.
  3. Wald, A. (1945). Sequential tests of statistical hypotheses. Annual Mathematica Statistics. 16, 117-186.
  4. MIL-HDBK-781A, Reliability Test Methods, Plans, and Environments for Engineering Development, Qualification, and Production.
  5. Epstein, B., & Sobel, M. (1955). Sequential Life Tests in the Exponential Case. The Institute of Mathematical Statistics.