The performance of a new product or process must be assessed regularly as it is developed, which requires using reliable objective tools to determine:
Whether recent changes have improved the performanceHow well the current performance satisfies customer requirementsWhich changes in input variables or their settings definitely influence the performance
The form of relationship (i.e., an equation) between influential input variables and critical performance characteristics.
In carrying out these tasks, we must be able to distinguish real changes in product or process performance from apparent changes that are really the result of random variation. The analytical tools described in this chapter are among the ...