Strength two covering arrays: Existence tables and projection

A covering array  CA(N;t,k,v)CA(N;t,k,v) is an N×kN×k array such that every N×tN×t sub-array contains all t  -tuples from vv symbols at least once, where t is the strength of the array. Covering arrays are used in experiments to screen for interactions among t-subsets of k components. Strength two covering arrays have been studied from numerous viewpoints, resulting in a variety of computational, direct, and recursive constructions. Consequently, it can be difficult to determine the smallest covering array that results from known construction. To address this, existence tables for the best currently known covering arrays are presented. In the process, a new direct construction from orthogonal arrays is also introduced.