Defines other settings affecting a What-If analysis.
Multi-Way What-If analyses vary inputs at the same time and calculate the effect of each combination of input values on results. When you have Multi forms of functions in your worksheets (VaryMulti, VaryMultiTable or @RISK functions in their Multi form, such as NormalMulti or DiscreteMulti), an analysis run using the What-If Analysis Run command will include a multi-way what-if analysis. When executing a Multi-Way What-If, TopRank first identifies all VaryMulti and VaryMultiTable functions in your spreadsheet. Then, using the Group Size entered, TopRank tries all combinations of input values possible. As with a one-way What-If, TopRank recalculates your spreadsheet for each combination and collects the new output values generated. Once the Multi-Way What-If is completed, TopRank ranks all calculated combinations according to their impact on each output. Multi-Way What-
100 What-If Analysis Menu Multi-Way What-If options include:
• Group Size. The number of inputs to be included in each combination tested in a Multi-Way analysis is determined by the Multi-Way Group Size setting. By default all VaryMulti and VaryMultiTable functions in a spreadsheetare included in a Multi-Way What-If analysis. For example, you might have four inputs defined using VaryMulti and VaryMultiTable functions — price, sales volume, production costs, and investment — and you want to see the impacts of every combination of two inputs on your result, profit. In this case, the Group Size is two. Your analysis might tell you that price and sales volume varying together are the most significant combination affecting your result — profit. Setting the Group Size to three might identify the combination of price, sales volume and investment as the most important three-way combination of inputs on results.
A Group Size of Auto forces the Group Size to equal the number of all VaryMulti and VaryMultiTable functions in a spreadsheet. Use this setting if you want to force TopRank to calculate every possible combination of input values.
Note: Group Size is a default entry that is set at the start of a Multi- Way What-If analysis. If you want Multi-Way What-If results with a different Group Size than was calculated in your current results, simply change the default Group Size and re-run the analysis.
• # of Steps. The # of Steps entry specifies the number of steps TopRank calculates across the minimum-maximum range of Vary and distribution functions during a Multi-way What-If analysis. A different default number of steps value is used for a Multi-Way What-If analysis as opposed to a standard one-way What-If analysis. Typically you want fewer Multi-Way steps as compared to one-way steps (the number of steps must be greater or equal to two). This minimizes the number of recalculations or iterations required to complete a Multi-Way What-If analysis.
Multiple runs can be executed for any What-If analysis in TopRank. When the # of Runs setting is greater than one, TopRank sequentially executes the desired number of What-If analyses one after another. Multiple runs are used to run several What-If analyses on the same model, using different assumptions for each analysis. Compare the results from each run to see the effect of the changing assumptions on the What-If results.
Assumptions can be changed by run by using the SIMTABLE function. Each run a new value is used for every SIMTABLE function in the model. The SIMTABLE function takes a list of values as arguments, such as:
=RiskSimtable({100,200,300,400})
Each run, the SIMTABLE function returns the argument whose position in the list is the run number. In the above SIMTABLE function, the value 100 is returned the first run, 200 the second and so on. The # of Runs defined should be less than or equal to the number of arguments entered into all SIMTABLE functions. If the number of runs is greater than the number of arguments entered into a SIMTABLE function, the SIMTABLE function returns an error value during a run whose number is greater than the number of arguments.
Refer to the @RISK Function Reference in the @RISK User's Guide for more information on using the Simtable function.
102 What-If Analysis Menu The Update Display option toggles on and off the updating of the worksheet displayed during a What-If analysis. For each iteration of a What-If analysis, a new value is returned for a Vary or VaryTable function and the spreadsheet is recalculated.
Update display shows the results of each recalculation on the screen (box checked) or suppresses the display (no check). Selecting the Update Display option causes What-If analyses to run slower. The Update Display setting can be changed while a What-If analysis is running by pressing the <Num Lock> key.
The Pause on Error setting pauses a What-If analysis if an error value is generated in any of the selected outputs during a calculation. When the analysis pauses, the output range containing the error value is
highlighted in the worksheet. Scroll about the worksheet to examine the combination of input values which leads to the error condition. Then, continue the simulation if you wish.