Template:Example: Median Rank Plot Example

Median Rank Plot Example

In this example, we will determine the median rank value used for plotting the sixth failure from a sample size of ten. This will be used to illustrate two of the built-in functions in Weibull++'s Quick Statistical Reference.

Solution

First, open the Quick Statistical Reference and select the Inverse F-Distribution Values option.

In this example, N = 10, j = 6, m = 2(10 - 6 + 1) = 10, and n = 2 x 6 = 12.

Thus, from the F-distribution rank equation:

[math]\displaystyle{ MR=\frac{1}{1+\left( \frac{10-6+1}{6} \right){{F}_{0.5;10;12}}} }[/math]

Calculate the value of F0.50:10:12 by using the Inverse F-Distribution Values option from the Quick Statistical Reference, or F0.50;10;12 = 0.9886 as shown next:

Consequently:

[math]\displaystyle{ MR=\frac{1}{1+\left( \frac{5}{6} \right)\times 0.9886}=0.5483=54.83% }[/math]

Another method is to use the Median Ranks option directly, which yields MR(%) = 54.8305%, as shown next: