This dissertation develops a cost rate with precise classification of cost activities into direct cost or overhead cost by using robust multiple regression, coefficient correlation, and moderator variable analysis. The accurate work center cost rate (WCCR) affects company leadership in pricing, continuous improvement of forecast resource demands, and scalable production. The source of inaccuracy of WCCR largely comes from mistakes in classifying the cost of nebulous activities such as scientists’ project supervision and engineering corroboration that are intertwined to be classified as direct cost or overhead cost, or the cost of the activities may be both overhead cost and direct cost. The predictive correlational study was used to classify the cost of the nebulous activities by measuring the coefficient correlation between the cost of nebulous activities and direct cost and overhead cost. The findings in the study posited that there is a strong correlation between the cost of the nebulous activities and the direct cost, but the correlation between the cost of the nebulous activities and the overhead cost is not significant. Analysis in the study has expanded the knowledge of cost classification in managerial accounting, and the statistical tool of predictive correlational study has filled the gap in cost rate modeling for aerospace manufacturing businesses.