A Safety-Deviation is a Measure of the estimated-or-observed difference between a required Safety-Margin, and the estimated or actual System Attribute Level.

Alternative Names

Concept Number: *405
English Master: Safety-Deviation
Synonyms, Variations & Acronyms: none


“How safe?” or “How safe compared to plan?”



Figure *405: Diagram showing calculation of a Safety-Deviation for a performance Attribute. The Safety-Margin is relative to the target Level and the distance between the Baseline and the target. In this example, as the required Safety-Margin is 150%, it must be 50% beyond the target Level. The distance (x) is worked out from the distance between the target and the Baseline (2x).


[Safety-Deviation *405]: Metric.




1. Each Scalar Attribute target (performance Goals and Resource Budgets) will potentially have its own computable value for Safety-Deviation.

2. Safety-Deviation expresses how far away the current design proposal, or Evo-Step implementation, is estimated to be from the desired safety Level. The higher the negative deviation is, the greater the “risk of failure” to deliver the target Level of the Attribute.

3. The Safety-Deviation can be used by technical management to monitor the progress of a design or a real Evolving project delivery. Management will need some Policy regarding setting and respecting Safety-Factors. They will need to set some Standards regarding the degree to which designs include planned Safety-Factors. This is a specific tactic for Risk management.

4. A Safety-Deviation is measured as a percentage difference between the estimated or actual Percentage-Impact and the Safety-Margin. Percentage values are usually used. It could however be expressed as the difference between the two Levels using the actual Units-of-Measure.

Safety-Deviation is calculation in a slightly different way for Cost Attributes, than for performance Attributes. because the value for the Safety-Margin is calculated in a different way.

Assuming percentage values are being used,

The calculation of Safety-Deviation for performance Attributes should be as follows:
(Percentage-Impact-Estimate or Percentage Actual Measure) – Safety-Margin

while the calculation of Safety-Deviation for Cost Attributes should be as follows:
Safety-Margin - (Percentage-Impact-Estimate or Percentage Actual Measure)

5. When using the Value-Decision method, and a spreadsheet model, the Safety-Deviation computations can normally be done automatically using the values of the Requirements and the design Impacts. Automatic warning of insufficient safety is a possibility.


[Safety-Deviation *405]: X.±



Safety-Deviation *405
Safety-Factor *131
Safety-Margin *637



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Created by system. Last Modification: Thursday 11 of July, 2019 20:23:16 CEST by Admin (Kai).

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