Characteristics of distribution – estimates of center and spread for Parametric Distribution Analysis (Arbitrary Censoring)

The Characteristics of Distribution table displays measures of the center and spread of the distribution.

The mean time to failure (MTTF) and the median estimates are measures of the center of the distribution, whereas the standard deviation and the interquartile range (IQR) are measures of the spread of the distribution.

Use these values only when the distribution fits the data adequately. If the distribution fits the data poorly, these estimates will be inaccurate. Use the distribution ID plot, probability plot, and goodness-of-fit measures to determine whether the distribution adequately fits the data.

Example output

Characteristics of Distribution Standard 95.0% Normal CI Estimate Error Lower Upper Mean(MTTF) 76585.0 488.710 75633.1 77548.8 Standard Deviation 15389.5 407.421 14611.4 16209.1 Median 77639.9 501.312 76663.5 78628.7 First Quartile(Q1) 66660.6 610.001 65475.7 67866.9 Third Quartile(Q3) 87554.2 543.215 86496.0 88625.4 Interquartile Range(IQR) 20893.7 591.844 19765.3 22086.5


The MTTF (76585.0) and the standard deviation (15389.5) are sensitive statistics because the tails in a skewed distribution and outliers significantly affect the values.

The median (77639.9) and the IQR (20893.7) are resistant statistics because the tails in a skewed distribution and outliers do not significantly affect the values.

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