A First Course in Quality Engineering, 2nd Edition

Quality in Design 173

with the heading “interaction,” added to those from Table 3�4� The original

columns with (−) and (+) signs are named “design columns,” and the new

column is called the “calculation column�” The treatment combinations are

identied by new codes: “(1)” for the treatment combination in which both

factors are at low level, “a” for the treatment combination in which Factor A

is at high level and Factor B at low level, “b” for the treatment combination

in which Factor B is at high level and Factor A at low level, and “ab” for the

treatment combination in which both factors are at high level� These codes

represent the average ...