One might wonder, however, just how accurate are the job costs calculated in Cornerstone 7.6? Is this amount the true cost of the product in question? Sine materials and labor are directly traceable to product, the accuracy of product costs depends largely on the accuracy of the assignment of overhead costs. This in turn depends on the degree of correlation between the factors used to allocate support service costs to departments and the factors used to allocate the department’s overhead cost to the products0 For example, if power costs are highly correlated with kilowatt-hours and machine hours are highly correlated a product’s consumption of the Grinding Department’s overhead costs, then we can have some confidence that the $5 overhead rate accurately assigns costs to individual products. However, if the allocation of support service costs to the Grinding Department or the use machine hours is faulty—or both—then product costs will be distorted. The same reasoning can be applied to Assembly Department. To ensure accurate product costs, great care should be used in identifying and using causal factors for both stages of overhead assignment.