The conventional design is listed in table 7 and the corresponding I-optimal design is listed in table 8. Table 9 summarizes the comparison of the two designs. The IV for the I-optimal design is also smaller. It is interesting to note that the conventional design here is D-optimal. D-optimal designs provide narrow confidence limits on the b coefficients, rather than on predictions.
Narrow confidence limits on predictions are more important in industrial experiments.
Summary Table 9 Conclusion This paper has shown I-optimal designs to be superior to conventional designs for industrial experiments using three real cases. I-optimal designs are superior because they give narrower confidence limits on predictions, on average, producing higher quality predictions of product performance. We supply I-optimal designs to all of our clients.