Calculations with No Data Entered

You can perform what-if analyses in Weibull++ even when the only information you have is the distribution and its parameters. When you calculate a Weibull++ standard folio that does not contain any data, the software will prompt you to specify parameters and then allows you to use the plots and QCP in the same way that you would for a calculated data set.

To do this, create a Weibull++ standard folio data sheet but do not enter any data. On the control panel, choose a distribution and then choose Life Data > Analysis > Calculate or click the icon on the Main page of the control panel.

With no data specified, this opens an input window containing two tabs:

The Parameters tab allows you to perform an analysis based on a set of parameters you specify. Enter your desired parameters and click OK to use those values in the analysis. You can use the plots and the QCP to obtain results based on the specified parameters. The parameters may or may not be based on an actual data set; therefore, the analysis is appropriate only within the context of the specified scenario.
The Options tab allows you to generate a data set based on a sample size, number of failures, probability and the parameters you have entered in the Parameters tab. Select the Add data and recompute check box to enable this feature, as shown next.

In the example shown, 6 out of the 10 units in the sample are failures and the probability estimate is set to 50%. This tells the software to obtain the rank of each failure based on the specified probability.

Note: The ranks can be found for any probability greater than zero and less than 1, but when the probability is 50%, the software computes the median ranks. The ReliaWiki resource portal has more information on median ranks at: http://www.ReliaWiki.org/index.php/Parameter Estimation.

When you click OK, the software will obtain the corresponding failure times of each rank based on the distribution and specified parameters, and then automatically recompute the parameters of the selected distribution based on the obtained failure times. The new parameters are displayed in the Analysis Summary area of the control panel. You can use the plots and the QCP to obtain results based on the recomputed parameters.