Evaluation of Orthogonally Blocked Central Composite Designs with Partial Replications

In this work, the orthogonal blocking of the central composite designs is evaluated by considering various equal and unequal replications of the centre point in the factorial (cube) and axial (star) blocks. The A-, D- and G-efficiencies as well as the V-criterion are the single-value design criteria used to examine the prediction performances of the designs. The fraction of design space plot is the graphical method used to display the prediction variance characteristics of these designs throughout the entire design space. The cube and star portions are also replicated to enhance the performance of the designs. The results show that higher and equal replication of the centre points in the blocks as well as more centre points in the star blocks than the cube blocks improve the prediction capabilities of the orthogonally blocked CCD in spherical region. © 2016, Indian Statistical Institute.