Suppose the Ashland Shakespeare Festival is hiring a new music director. The group gives all applicants for the position three tests: (1) a work-sample test, in which each applicant is asked to score a scene from As You Like It and a scene from Richard III; (2) a conducting test, in which each applicant is asked to conduct the brief section from Franz Schubert's, String Quartet No. 10 in E-flat Major, D. 87, Scherzo; (3) a performance test, in which each applicant is asked to play a selection of classical music on the instrument of his or her choice. Each test has to be passed at the 80% or above level for the applicant to be considered as a candidate for the position of musical director. What approach to combining predictors is the Ashland Shakespeare Festival using?