This is just an Excerpt from a larger document, click here to view the entire document.Similar Item/Circuit Prediction
This method starts with the collection of past experience data on similar products. The data is evaluated for form, fit and function compatibility with the new product. If the new product is an item that is undergoing a minor enhancement, the collected data will provide a good basis for comparison to the new product. Small differences in operating environment or conditions can be accounted for by using translation methods based on previous experiences. If the product does not have a direct similar item, then lower level similar circuits can be compared. In this case, data for components or circuits is collected and a product reliability value is calculated. The general expression for product reliability calculated from its constituent components using the similar item method is:
Rp = R1 · R2...Rn
Rp = Product reliability
R1, R2 ...Rn = Component reliability
The advantage to using the similar item prediction method is that it is the quickest way to estimate a new product's reliability, and is applicable when there is limited design information e.g., very early in the design phase. The disadvantage is the possibility that the new product will actually be substantially different from the similar item, resulting in incorrect or inaccurate predictions.