74 NORMAN R.DRAPER AND IRWIN GUTTMAN this is every column which contains a"1"in the first apec23%23et5 ate with a"2"in the first parts).One more set of four osen.Again,however,there are very many po e to us.These and other General 2k-P Fractional Factorial Links Defined by (c12.c13.c24.and c34) 2l2=-1-2+3十1=C13+C24=C14+C23 with 2 212=1-2-为+4=-012+c34=-C13+c24 pa and Hunter Illustrative Example to reduce sweing both feet connected figures which link the four points. Th ral gai making any of the three sets of paired comparison even if individual observations are tainted by block tation.In this constructed,but fact-motivated exam ple.two manufacturers,coded as U and G.each ofer ny CE The 21 Design GE,(3)UB,()GB are thus the four corners of a 2 Tn之 s shown in Figure een their B The issue for table of signs(e.g.Box,Hunter.and Hunter (197 (1+234).the (possibly important)main effect of fac tor I plus the (w of signs designated 1=234 to attach to the corre by the diviso Then itis for example.that knowledge 名=-1 3 =1 f signs. (Note that FIGURE 4.The21 Design Defined by /-1234. Journal of Quality Technology Vol.29,No.1.January 1997 Reproduced with permission of the copyright owner.Further reproduction prohibited without permission.Reproduced with permission of the copyright owner. Further reproduction prohibited without permission