Managing for Quality and Performance Excellence 9th Edition by James Evans,William Lindsay

Exercise 41

During one month, MegaInvCo (MIC) processed 51,000 invoices for Alpha Corp, 49,000 for Beta Corp, and 25,000 for Gamma Corp. Of these, 510 of the Alpha, 525 of the Beta, and 480 of the Gamma invoices had to be reprocessed for errors. What is the overall defect rate and the sigma level for all of the combined batches? For each individual batch?