Contents - Index

Output Variable Dialog Box





The Output Variable dialog box is used to enter and change information concerning an output variable.  It is one of four variable dialog boxes.  The dialog controls are:
Symbol edit box:
Used to enter a unique symbol to represent the output variable in equations.  It can be any combination of letters, the digits 0-9 and underscores so long as the first character is not a digit.  It can be of any length but is best limited to 1-4 characters.
Name edit box:
Used to enter a more detailed name or description of the output variable.  It can be any combination of characters and any length.
Units edit box:
Used to enter the units of measure associated with this output variable (optional).  Can be any combination of characters and any length.
Precision button:
Displays popup menu for specifying precision to display tolerances in Capability Study window, Pareto Chart window, Summary Table window and other child windows.   Default is 5 significant digits.  Can be used to specify either the number of significant digits or the number of digits after the decimal point.
Equation edit box:
Used to enter an equation representing the effect of the inputs on this output.  Must be a valid expression.  This equation can include the symbols of the continuous input variables and other output variables.  For output variables, recursive or circular references are not allowed.
The equation can also include categories of category input variables of the form "Variable Symbol { Category Symbol }".  This reference has the value 1 when the given category is the selected category and a value of 0 when it is not.  Categories are selected using the Category Input dialog box.
While an equation can be directly typed into the Equation edit box, it is generally simpler to enter it using the Keyboard Equations dialog box.  To display the Keypad Equations dialog box, click the Keypad button.  You can also paste an equation from some other program using the Paste Equation dialog box.
Constraints can also be specifying as part of the equation.
Target edit box:
Used to enter the target if one exists.  Leave blank otherwise.  Must be a valid constant expression.  The target is needed to calculate the distance from target.  The target must be between the lower and upper specification limits, if they exist.
Lower Spec Limit edit box:
Used to enter the lower specification limit if one exists.  Leave blank otherwise.  Must be a valid constant expression.  The lower specification limit is needed to calculate Cp.  Either the lower or upper specification limit is needed for Cpk, the defect rate, Z-score, sigma level and the distance inside spec.  The lower specification limit must be below the target and upper specification limit, if they exist.
Upper Spec Limit edit box:
Used to enter the upper specification limit if one exists.  Leave blank otherwise.  Must be a valid constant expression.  The upper specification limit is needed to calculate Cp.  Either the upper or lower specification limit is needed for Cpk, the defect rate, Z-score, sigma level and the distance inside spec.  The upper specification limit must be above the target and lower specification limit, if they exist.
Method of Estimating Average and Standard Deviation list box:
VarTran derives equations for the average and standard deviation of the output based on the equations entered.  There are two basic approaches used: curve fit and Taylor series.  Both approaches locally approximate the equation by a polynomial for which the average and standard deviation can be derived.  The Taylor series approach uses Taylor series expansions to generate the polynomial.  The curve fit approach fits a curve through specific points.  The Taylor series approach is generally faster to execute but requires continuously differentiable functions so is not applicable when the following functions are used: Minimum, Maximum, and AbsoluteValue.  The higher the order used, the better the approximation but the longer the execution time.  A first order corresponds to fitting a straight line, second order to fitting a quadratic polynomial, etc.  The default is second order Taylor series approach.
Include in Optimization With Multiple Outputs check box:
When using the Find Optimal Targets dialog box and there are multiple outputs, one has an option to optimize all outputs.  This option will construct an objective function to optimize that includes all the output functions that have the Include in Optimization With Multiple Outputs check box checked.  The default is to check this box.  If you wish to exclude an output from the optimization, remove the check mark.  Some outputs might represent intermediate calculations used by other outputs and not be appropriate for use in the optimization.  Other times, you may wish to exclude outputs of lesser importance that appear to prevent other more important outputs from reaching acceptable values. 
As you enter information, the status bar at the end of the program is automatically updated to reflect any errors.  Other child windows are notified of the changes as well and will update themselves according to the update mode selected on the Options menu.  The updates occur when the focus is transferred to another control by clicking on some other control or by pressing the Tab or arrow keys.   
Based on the equation entered, VarTran derives equations for both the average and standard deviation of the output variable.  These equations are evaluated to obtain the values of the average and standard deviation that appear in the Capability Study window.  To view these derived equations, click the View Eq. button.  This displays the View Equation dialog box showing the equations.

To close the dialog box and save the changes, click the OK button.  To cancel the changes including the addition of a new variable, click the Cancel button, press the Esc key or click the X in the upper right corner of the dialog box.  To delete the variable, click the Delete button.  For help, click the Help button or press the F1 key.