This is just an Excerpt from a larger document, click here to view the entire document.Worst Case Analysis
Worst Case Analysis and the electronic specific Worst Case Circuit Analysis (WCCA) consider the impact on desired performance of expected variations in part parameters. For example, a WCCA could determine whether or not the frequency of a radar transmitter would be within specifications if the parameters of parts used were at unfavorable "off-nominal" values. The most conservative worst case analysis calculates product performance with all parts at their worst value and causing errors in the same direction. This is known as extreme value analysis and is the easiest approach. Other approaches are root-sum-squared and Monte Carlo analysis which considers the statistical distribution of variables, recognizing that random variations of different parts are rarely all at extreme values in the same direction and that one variation can offset another. These more realistic approaches are more difficult to perform, but are important when the penalties of designing for the extreme value are too severe to make it practical. In any event, parts are selected so that their expected variations do not preclude acceptable product operation, as determined by the method used. WCCA is discussed in the Reliability Toolkit: Commercial Practices Edition. More detailed treatment may be found in the RIAC publication, Worst Case Circuit Analysis Application Guidelines. Finite element analysis (FEA) is a computer technique invented for analyzing stresses in mechanical and structural assemblies (and now also widely used in electronic stress analysis).
