Reliability HotWire: eMagazine for the Reliability Professional
Reliability HotWire

Issue 57, November 2005

Tool Tips

* Which degradation model should be used in Weibull++ 7s Degradation Analysis Folio?

Weibull++ 7 makes it easy to select the degradation model that best fits your data. Once you have entered the data into the Data Sheet, select Model Wizard from the Data menu or click the Degradation Model Wizard icon.

On the Main page, select the models you want to consider and click Analyze.

When the analysis is complete, the rankings of the models will appear beside them and the highest ranking model will be highlighted. In addition, the Analysis Details page becomes available. The Ranks sheet of the Analysis Details page displays the overall ranking of the models as well as the ranking of the models for each Unit ID.

The MSE sheet of the Degradation Model Wizard displays for each model an overall Mean Square Error (MSE) value and an MSE value for each Unit ID. These numbers provide a measure of how closely the model fits the data points by taking the sum of the squares of the X and Y differences between each point and the fitted line. The lower this number, the better the fit.

You can implement the highest ranking model by clicking Implement.

* How can cells, Data Sheets and formulas be referred to quickly in Weibull++ 7?

To define a variable name for a cell, for a Data Sheet in any Standard Folio in the project or for a function, select Define Name from the Sheet menu or click the Define Name icon.

The Defined Names window will appear, as shown next.

The Defined Names window displays a table of all defined variable names for the current Folio or Report. You can type the definition manually or you can choose to set it automatically. Clicking Active Cell(s) defines the variable name to the currently selected cell(s) in the sheet. Note that you can select new cells in the sheet while the Defined Names window is open. Clicking Data Source opens the Select Folio/Data Sheet window, which allows you to select a Data Sheet in any Standard Folio as the definition of the variable name. In the picture shown here, the defined variables represent a cell, a Data Sheet and a formula, respectively. Note that the formula refers to another defined variable.

To refer to a cell or Data Sheet with a variable name, you can type the name into the cell as a function, e.g. if the name is "Test" then type =Test into the cell. Variable names can also be used as input for functions. For example, if "Cell" is a variable name representing a cell, =COS(Cell) returns the cosine of the value of that cell. If "Sheet" is a variable name representing a Data Sheet, =DISTR(Sheet) returns the distribution used by that Data Sheet.

The variable names you define in a Data Sheet or General Spreadsheet will be available for use in any Data Sheet or General Spreadsheet within the current Standard Folio. The variable names you define in a Report Sheet will be available for use in any Report Sheet within the current Report.

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