=+21. Because processes are designed to produce products with fixed nominal dimensions, it is quite common to find that most of the variation in sample data occurs in the rightmost one or two decimal places. For example, the following data comes from a process making parts whose nominal length is required to be .254 inch:

Subgroup x1 x2 x3 Subgroup x1 x2 x3 1 .258 .254 .256 11 .253 .257 .254 2 .253 .251 .253 12 .252 .253 .258 3 .252 .258 .256 13 .258 .253 .257 4 .252 .252 .255 14 .251 .257 .256 5 .254 .252 .256 15 .256 .254 .257 6 .253 .254 .256 16 .251 .255 .253 7 .251 .257 .257 17 .252 .256 .255 8 .252 .251 .255 18 .251 .256 .253 9 .251 .255 .257 19 .253 .252 .254 10 .257 .255 .255 20 .255 .252 .253