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Binomial Confidence Intervals

This tool calculates one-sided and two-sided confidence intervals for discrete reliability test data (i.e., go/no-go testing). Given a risk (α), confidence is calculated at the 1-α level for the true proportion defective p, where Nd defects are found in a sample size of N. For additional details, click here.

The tool is prefilled with example data from the NIST Engineering Statistics Handbook. See the example shown at the bottom of this page.

Calculation Inputs:

1. Sample size (N):
2. Number of defects found (Nd):
3. Confidence:
4. Decimal places:
5. Output:
6. Chart:

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  5. O'Connor, Patrick, D. T., Practical Reliability Engineering.
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  8. Khan Academy, Margin of Error 2.
  9. Khan Academy, Confidence Interval Example.