# Local Sensitivity and Sensitivities: what difference?

Member Posts: 16

In DX we have 2 types of sensitivities:

Local Sensitivity

It is available in the Response Surface component. It represents the variation of an output parameter when a single input parameter varies, with all the other inputs to their current value (current Response Point).

The variation of the output is simply calculated (if Axes Range = Use Min Max of the Output Parameter): (sign) 100 * one-parameter-varying range / all-parameters-varying range

The sign is determined whether the Min happens before or after the Max.

For example, let's look at this curve:

When only P1 varies:

Deformation Max = 2.024

Deformation Min = 0.0684

When all parameters vary (results from Min-Max Search):

Deformation Max = 2.36

Deformation Min = 0

The max happens for a smaller abscissa than the min. So we give a negative sign to the variation. So, Local Sensitivity = - 100 * (2.024 - 0.0684) / (2.36 - 0) = - 82.86 %

That's what we see on the Local Sensitivity chart for P1 vs P4:

This value is "local" because it changes if we change the value of the other input parameters (except if everything is perfectly linear).

Note: If we change Axes Range to Use Chart Data, the chart bars are then normalized based on the longest bar for each output parameter, instead of using all-parameters-varying range.

Sensitivities

It is available for Optimization, Six Sigma and Correlation components. This is a correlation calculation (Spearman). It is based on the points which were evaluated in Optimization (for example, 1000 Screening points), Six Sigma (LHS) or Correlation (LHS). It is bounded to [-1; 1].

The Spearman correlation is calculated as following:

Sometimes, some values may be set to 0 due to the "Significant Level". If you set this significant level to 1 (in Tools > Options > DX), then you should not see these zero values anymore.

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