“…Second, these tasks were placed into quartiles of learning difficulty (Mumford, Weeks, Harding, & Fleishman, 1987) on the basis of task inventory data. Third, tasks were randomly selected within quartiles with the restriction that 40% of the tasks be selected from the fourth (most difficult) quartile, 30% from the third quartile, 20% from the second quartile, and 10% from the first (least difficult) quartile (Lipscomb, 1984).…”