Four readily available second-order small response surface designs for three-factor experiments are examined and compared in order to find an alternative design for experiments with limited resources. In this paper, the prediction variances of Roquermore's three-factor hybrid designs and Draper-Lin's small composite design are investigated over the experimental region using box plot and fraction design space (FDS) plot. For each spherical region, the replication of center and axial points are compared. The Box plot and Fraction Design Space plot shows that increasing the number of center and axial points will result in a decrease of standard error of D311B; will also result in a more stable prediction variance and will also decrease the spread of dispersion of the prediction variance. These results suggest that D311B is more efficient and is preferable for three-factor experiments with inadequate resources.
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Keywords: Axial and center points; Draper-Lin small composite design; Fraction design space plot; Roquermore hybrid designs
Biography: Virjil, a practicing statistician, has been collaborating scientific researches for almost a decade. Most of his collaborations were in the field of renewable energy, materials science and biotechnology. His interest is response surface methodology and is currently one of the research collaborators of the Commission on Higher Education - Zonal Research Center Grant in Aid project. He is currently teaching mathematics and statistics at the University of San Carlos, Cebu City, Philippines.