Template:Example: Weibull Disribution Unreliability RRX Example

Weibull Distribution Example 8

What is the unreliability of the units in Example 1 for a mission duration of 30 hours, starting the mission at age zero? To replicate the results in this reference with Weibull++, choose RRX (Rank Regression on X) as the calculation method.

Solution to Weibull Distribution Example 8

First, use Weibull++ to obtain the parameters using RRX.

Then, we investigate several methods of solution for this problem. The first, and more laborious, method is to extract the information directly from the plot. You may do this with either the screen plot in RS Draw or the printed copy of the plot. (When extracting information from the screen plot in RS Draw, note that the translated axis position of your mouse is always shown on the bottom right corner.)

Using this first method, enter either the screen plot or the printed plot with T = 30 hours, go up vertically to the straight line fitted to the data, then go horizontally to the ordinate, and read off . Then, a good estimate of the sought unreliability is 23%. (Also, the reliability estimate is 1.0 - 0.23 = 0.77 or 77%.)

The second method involves the use of the Quick Calculation Pad (QCP). To activate the Quick Calculation Pad either click its icon on the Data Analysis toolbar, or Data Folio Control Panel

or select it from the Tools menu. Once activated, the QCP will appear on your desktop. Switch to the Basic Calculations page of the QCP, select Std. Prob. Calculations from the Options For Calculations box, and enter 30 hours in the Mission End Time box, making sure that the Results as Probability of Failure option is selected in the Results Option box.

Click Calculate to get the result. The result is shown in the figure above, or Note that the results in QCP vary according to the parameter estimation method used. The above results are obtained using RRX.