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 Error	95% Normal CI
Distribution	Mean	Standard 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.