If you buy more than one of an item used in your product, you will have to deal with variability. In general, the variability from part to part is minimal and expected. Occasionally, the variability is large and causes reliability problems.

According to O’Connor and Kleyner, “The main cause of production-induced unreliability, as well as rework and scrap, is the variability inherent in production processes.” O’Connor, Patrick D. T. and Andre Kleyner. 2012. Practical Reliability Engineering. Chicester: John Wiley and Sons. Web. Continue reading →