Tham khảo tài liệu 'engineering statistics handbook episode 7 part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | . Alternative foldover designs Alias patterns and effects that can be estimated in the example design The two-factor alias patterns for X4 are Original experiment X4 X1X2 X3X7 X5X6 Reverse X4 foldover experiment X4 -X1X2 -X3X7 -X5X6. The following effects can be estimated by combining the original with the Reverse X4 foldover fraction X1 X3X5 X6X7 X2 X3X6 X5X7 X3 X1X5 X2X6 X4 X5 X1X3 X2X7 X6 X2X3 X1X7 X7 X2X5 X1X6 X1X4 X2X4 X3X4 X4X5 X4X6 X4X7 X1X2 X3X7 X5X6 Note The 16 runs allow estimating the above 14 effects with one degree of freedom left over for a possible block effect. Advantage and disadvantage of this example design The advantage of this follow-up design is that it permits estimation of the X4 effect and each of the six two-factor interaction terms involving X4. The disadvantage is that the combined fractions still yield a resolution III design with all main effects other than X4 aliased with two-factor interactions. Case when purpose is simply to estimate all two-factor interactions of a single factor Reversing a single factor column to obtain de-aliased two-factor interactions for that one factor works for any resolution III or IV design. When used to follow-up a resolution IV design there are relatively few new effects to be estimated as compared to 2jj designs . When the original resolution IV fraction provides sufficient precision and the purpose of the follow-up runs is simply to estimate all two-factor interactions for one factor the semifolding option should be considered. Semifolding http div898 handbook pri section3 2 of 3 5 1 2006 10 30 44 AM . Alternative foldover designs Number of runs can be reduced for resolution IV designs For resolution IV fractions it is possible to economize on the number of runs that are needed to break the alias chains for all two-factor interactions of a single factor. In the above case we needed 8 additional runs which is the same number of runs that were used in the .
