Gatlin Education Six Sigma Green Belt - OVERVIEW Why Do Six Sigma - Page 13

Yield for Processes in Series When we have processes in series, it's interesting to note how quickly the defect rate deteriorates. Say for example that an order is processed through six departments, each with the defect rates as shown in the Slide. The yield of each of these processes (that is, the useful output) is simply 1 minus the defect rate, so for example the first process has a yield of 1 minus 0.3 percent, or 99.7 percent. We can calculate the final yield of these processes by multiplying the yields of the individual processes. Note how the final yield in this case is 71.4 %, significantly worse than any of the individual processes. We then convert the 71.4 % final yield to its equivalent 28.6% defect rate, and in the same manner as shown in the prior examples convert that to a Sigma Level of 2.