Sensitivity Analysis--Graphical Output

Program Name:
FCICHART has been developed for use with Quattro Pro v. 6 and Excel v.4 by the U.S. Army Engineer Waterways Experiment Station, Environmental Laboratory.

Audience:
FCICHART is intended to be used by Assessment teams (A-teams) who are developing aggregation equations for calculating a functional capacity index (FCI).

Purpose:
This spreadsheet assesses the influence of a single model variable on the FCI. It allows the user to input a model equation containing between 1 and 15 model variables. It then determines the change in the FCI by varying the subindex value of a single environmental variable from 0 to 1 while holding all other environmental variables (non-ncremented variables) constant. The process is repeated three times as the subindex value of the non-incremented variables are varied (1, 0.5, 0.1).

Use:
Within the spreadsheet, there are four steps that must be completed by the user. They are as follows:

  • Step 1. In cells C4-C18, the user must enter the name of each variable in the model. Up to 15 variables may be examined within each model. If there are fewer than 15 variables in the model, remaining cells should be left blank
  • Step 2. In cell C23, the user must enter the model equation. Care must be taken to input the equation in the correct Quattro Pro or Excel format, taking special note of variations in different versions of Quattro Pro.
  • Step 3. In cell C29, the user must enter the cell location (from step #1) of the variable to be examined (C4-C18). In cell C30, the name of the variable to be examined must be entered. The contents of cell C30 will be used as the name of the chart produced by this macro. NOTE: The user must take care to rename the chart with every run, or delete the current chart with the same name. Attempts to create a chart with the same name as a previously created chart will result in an error.
  • Step 4. Finally, the user must press the "Run Macro" button located at cells F33-G35.

Output:
A graph will appear with the title entered by the user from cell C30 of the worksheet. The graph shows the FCI value along the Y-axis and the sub-index value of the variable chosen in Step 3 along the X-axis. The three lines, as shown in the legend, indicate the three variations of the non-incremented variable values. REMINDER: Most errors here are due either to entry of invalid equations in cell C23 or to the re-use of old chart names in cell C30.

Interpretation of Graph:
The output graph determines how the FCI changes when a single environmental variable is varied from 0 to 1, while all other variables are held constant. The steeper the slope of the line, the greater the influence of that environmental variable on the resulting FCI value (when non-incremented variables are held constant).

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Web Date: October 1997
Updated: April 2008