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Page 51
Evaluation Criteria Table
Criteria description
Worst
Best
Quality
Relative
Sample 1
reading
reading
Characteris
Weighting
Readings
tics
Taste
0
12
Bigger
55 %
11
Moistness
25
45
Nominal
30 %
44
Number of Voids
8
Smaller
15 %
3
2
O E C = > 91.41
Overall Evaluation Criteria(OEC)
Example: Test Sample for Trial 1, Run 1
Before combining readings of all criteria, each reading is made dimensionless by dividing by a reference number,
which is the difference of the Worst and the Best reading. To avoid complication due to SIGN changes, absolute
values are used. To make logical meaning out of adding two numbers, their QC’s must also be of the same kind. Both
Smaller and Nominal(which becomes Smaller when deviation from the nominal is used) QC’s are transformed to act like
Bigger QC by subtracting the fraction contribution from 1. Each criteria contribution are then multiplied by their
respective relative weighting to for the OEC. Since all criteria have been made to behave like the Bigger QC, the QC for
OEC is now Bigger is better. The decision about whether the OEC is made to have Bigger or Smaller QC depends on
the cumulative percentages of all criteria with Bigger QC(over 50 or not).
(OEC)11
| 11 - 0 |
| 44 - 45 |
|3 - 2|
= ( ----------------- ) x 55 + ( 1 - ------------ ) x 30 + (1 - -------------- ) x 15
| 12 - 0 |
| 45 - 25 |
|8 - 2|
= (11/12) x 55 + ( 1 - 1/20 ) x 30 + ( 1 - 1/6 ) x 15
= 50.41 + 28.5 + 12.5
= 91.41
Likewise OEC for all runs in all trials are calculated. The Quality Characteristic(QC) for OEC is Bigger is better as all
criteria have been switched to align their QC to match that of the Taste. This is done by (1 - fraction contribution), etc.
Note that there can be only one OEC (or RESULT) for a single sample and that the OEC calculated for each sample
becomes the sample RESULT, which are then be used to carry out the analysis and to determine the optimum
condition.
Nutek, Inc.
Qualitek-4, Automatic Design and Analysis of Taguchi Experiments
Reference Manual
Version: 06.01