Reference

　Orthogonal arrays are structured tables with the property that all combinations of factor levels occur an equal number of times between any pair of columns. They are used as fundamental tools for improving the effectiveness and efficiency of experiments in Robust Quality Engineering and Design of Experiments.

An orthogonal array is a tabular tool used in experimental design (particularly the Taguchi method) to efficiently organize and implement combinations of multiple factors (variables) and their levels. Each column represents a different factor, and each row represents a specific combination of levels for that factor (i.e., experimental conditions). The array is designed to enable a balanced evaluation of the effects between factors. This enables a rational experimental design that allows for the analysis of the main effects of factors with fewer experiments compared to a full-scale experiment that tests all combinations. There are various types of orthogonal arrays, and they are selected based on the number of factors and levels.