Reliability HotWire

Issue 89, July 2008

Tool Tips

* How can I compare data sets in Weibull++ 7?
Weibull++ 7 provides several ways to compare data sets.

  • Tests of Comparison: The Comparison Wizard allows you to compare two data sets to determine whether items from the first set will outlast those of the second. To access the Comparison Wizard, select Tests of Comparison from the Tools menu or click the Tests of Comparison icon.

From the drop-down menus in the middle of the Comparison Wizard, select the Standard Folio Data Sheets that contain the data sets you would like to test. When you click Compare, the message box at the top of the page returns the results and the Comments Box at the bottom of the page displays comments on the test, as shown next.

  • Plotting: The MultiPlot allows you to place more than one data set on a plot. Select Add Additional Plot then MultiPlot from the Project menu to add a new MultiPlot to the project. In the Select Folio/Data Sheet window that appears, select the calculated Standard Folio Data Sheets or Warranty Folio Data Sheets that contain the data sets you would like to compare then click OK.

  • Simple Plotting: One popular graphical method for making this determination involves plotting the data with confidence bounds and seeing whether the bounds overlap or separate at the point of interest. This can be effective for comparisons at a given point in time or a given reliability level, but it is difficult to assess the overall behavior of the two distributions, as the confidence bounds may overlap at some points and be far apart at others.

  • Contour Plotting: By overlaying two contour plots from two different data sets (analyzed using the same distribution) at the same confidence level(s), you can visually assess whether the data sets are significantly different at the given confidence level(s). If there is no overlap on the contours at a particular confidence level, the data sets differ significantly at that level. The disadvantage of this method is that the same distribution must be fitted to both data sets. In the figure shown next, failure data from two designs have been analyzed using the 2-parameter Weibull distribution. There is an overlap at the 95% confidence level and no overlap at the 90% confidence level, indicating that the new design is better at the 90% confidence level.

* How can I obtain a picture of my Xfmea/RCM++ System or FMEA Hierarchy that can be inserted into other documents?
Two recently-added options in Xfmea and RCM++ allow you to quickly and easily obtain a picture of a portion of your System Hierarchy Panel or FMEA Hierarchy Panel that can be inserted into other documents:

  • Select Copy System Panel as Graphic from the Edit menu to copy the currently visible contents of the System Hierarchy panel to the clipboard as a graphic

  • Select Copy FMEA Panel as Graphic from the Edit menu to copy the currently visible contents of the FMEA Hierarchy panel, in either the hierarchy view or the worksheet view, to the clipboard as a graphic.

The contents of the clipboard can then be pasted into other applications, such as graphics editors or Microsoft Word. Note that the entire visible area within the System Hierarchy panel or FMEA Hierarchy panel will be copied and that any items that are not currently visible will not be copied.

Copyright 2008 ReliaSoft Corporation, ALL RIGHTS RESERVED