STEM help / Data dialogs

Sensitivity / Parameters

By default, when a sensitivity is run, each parameter is varied up and down, with no intermediate steps. However, you can change this behaviour for all parameters within a particular Sensitivity element by changing the Steps and Perturbation settings in the Parameters dialog. When the value of a parameter is increased or decreased, this is normally calculated as a proportion of the original value (by default 1%). In the Details dialog, you can change the proportion used, or calculate the change on a different basis altogether (e.g., taking a specific value).

Generation

Steps

Controls the number of sets of intermediate sensitivity results that will be generated. With the default setting of 1, STEM varies the parameter with no intermediate steps (that is, calculates only one set of sensitivity results in each direction, up and down). However, if you want to examine the impact of the parameter in more detail, you can generate sets of results for several steps in each direction (up to a limit of 20 steps).

Note: changing the number of sensitivity steps to 2 does not double the maximum range. The number of steps is intended as a measure of detail, whereas the Up and Down values are intended as the overall limit independent of the number of steps.

See 9.4 Using sensitivities to identify critical model assumptions.

Default: 1.

Perturbation

Determines the direction in which the parameter is varied. By default, a parameter is perturbed both up and down (Bidirectional), but you can choose to vary it in a single direction (Unidirectional) – in which case only the Up value is used (note that this value can be entered as a negative figure).

See 9.4 Using sensitivities to identify critical model assumptions.

Default: Bidirectional.

Parameters

Parameter 1, Parameter 2

A reference to any numeric input.

See 9.3 Working with scenarios and 9.5 Managing complexity with template replication.

Default: none.

 

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