Table of MTTF for Distribution ID Plot (Right Censoring)

The MTTF (mean time to failure) is the expected amount of time that an item will function before failure.

Sometimes it may be difficult to determine the best distribution based on the probability plot or goodness-of-fit measures. Use the table of MTTF to compare the MTTF for several selected distributions to see how your conclusions change depending on the distribution that you select.

If several distributions provide a reasonable fit to the data and similar conclusions, then the choice of the distribution is less important.

However, if your conclusions differ depending on the distribution, you may want to report the most conservative conclusion, collect more data, or use additional information, such as process knowledge and expert advice.

Example output

Table of MTTF Standard 95% Normal CI Distribution Mean Error Lower Upper Weibull 64.9829 4.6102 56.5472 74.677 Lognormal 67.4153 5.5525 57.3656 79.225 Exponential 80.5676 13.2452 58.3746 111.198 Normal 63.5518 4.0694 55.5759 71.528

Interpretation

Based on a lognormal distribution fitted to the engine windings data, the engine windings can be expected to survive, on average, until 67.4153 hours.

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