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Statistical Issues in Defense Analysis and Testing Summary of a Workshop (1994) / Chapter Skim
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PITFALLS OF HYPOTHESIS TESTING
Pages 33-37

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From page 33...
... For example, a device may be required to have an expected lifetime of 100 hours. With standard assumptions e.g., that device lifetimes are well-modeled by an exponential distribution one can determine, for a given sample of units, how long the sample average lifetime must be in order to conclude, at some significance level, that the device's expected lifetime is not less than 100 hours.
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From page 34...
... , because test results are examined before deciding whether more testing is required. In this situation, the sequential nature of the tests usually is not recognized and hence the nominal significance level is not adjusted, resulting in tests with actual significance levels that are different from the designed levels.
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From page 35...
... Also, these tests avoid the complication posed by the multiple looks that investigators have had on a sequence of test results and the impact of that on nominal significance levels. Unfortunately, sequential methods may be difficult to use in OT&E, because there are times when the results of previous operational tests will not be known before the next test is ready to begin.
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From page 36...
... In reliability theory, nonparametric inferences typically involve a qualitative assumption about how systems age (i.e., the system failure rate) or a judgment about the relative susceptibility to failure of two or more systems.
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From page 37...
... discuss methods for displaying information and accounting for uncertainty when making decisions. Such techniques can allow human judgment to be combined with formal test procedures.
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Key Terms

  • hypothesis testing
  • hypothesis test
  • significance tests
  • confidence intervals
  • sequential methods

  • expected cost
  • mean lifetime
  • decision analysis
  • nominal significance
  • standard hypothesis

  • sequential tests
  • required level
  • significance level
  • significance levels
  • formal sequential

  • defense testing
  • average lifetime
  • allow human
  • maximum acceptable
  • clinical trials

  • participants urged
  • frequently leads
  • typically involve
  • unit costs
  • using significance

  • statistical terms
  • strict hypothesis
  • developmental tests
  • designs using
  • device lifetimes


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