The Accountant Scale of the Strong Interest Blank for Men bears little direct relation to a criterion of freshman engineering grades. However, it may act as a suppressor variable in conjunction with the Banker or Psychologist Scale of the Strong. It may also act as a moderator variable in conjunction with the Math.-Science Teacher or Real Estate Salesman Scale. These effects are illustrated by results obtained in two engineering schools. The basic algebra and geometry of moderator variables is given.