Purpose of the Tornado Diagram add-in

Tornado diagrams graphically display the result of single-factor sensitivity analysis.  A typical diagram looks like Figure 1, which shows the effect of four parameters on the result.  The uncertainty in the parameter associated with the largest bar, the one at the top of the chart, has the maximum impact on the result, with each successive lower bar having a lesser impact.

Figure 1

The y-axis corresponds to all the uncertain parameters being at their respective nominal, or base, values.  For each of the uncertain decision parameters, the chart contains one horizontal bar and two sets of numbers, one of the left and the other to the right of the bar.  Each set of numbers corresponds to the result value (upper number) and the value of the parameter at which the result value was reached (the lower number within curly brackets).  Negative numbers are shown in parenthesis.