Background
A particular component can fail due to six independent primary failure modes: A, B, C, D, E and F. The component fails if mode A, B or C occurs. If mode D, E or F occurs alone, the component does not fail; however, the component will fail if any two (or more) of these modes occur (i.e. D and E; D and F; E and F).  The objective is to analyze each data set using the 2-parameter Weibull distribution with MLE and to determine the lower 1-sided 90% confidence interval on the reliability of this component at 100 hr.

Experiment and Data
The following tables present the time-to-failure data for these modes (in hr).

Analysis
Step 1: Using Weibull++ 7, the first step is to create a new Data Entry Spreadsheet to hold grouped times-to-failure data with suspensions.

Step 2: Rename the Folio to "Component" and the Data Sheet to "A", enter the data given for Failure Mode A and use the 2-parameter Weibull distribution with MLE to calculate the parameters, as shown next.

Step 3: Insert another data sheet of the same type named "B," enter the data given for Failure Mode B and calculate the parameters. Repeat for the remaining failure modes.

Step 4: Select Add Diagram from the Project menu to add a Diagram to the project that contains a template block for each data sheet in the project, as shown next.

Step 5: Build the RBD that describes the reliability-wise configuration of the failure modes, as shown next.

Step 6: Click Calculate to analyze the Diagram, then use the Quick Calculation Page to calculate the reliability at 100 hr with the lower 1-sided 90% confidence bound, as shown next.