According to the 2008 J.D. Power and Associates Reports, Porsche models have the fewest quality problems in the industry, with just 87 problems per 100 vehicles. Infiniti and Lexus products follow with 98 and 99 problems per 100 vehicles.

a. Using the calculator at www.isixsigma.com/sixsigma/six_sigma_calculator.asp (last accessed 6/2/09), calculate defect percentage, process percentage, and process sigma for each of the three companies.

b. Why is the information provided by these calculations not totally helpful?