What is costing system refinement? what are the three guidelines for refinement? costing system refinement a. means making changes to a simple costing system that reduces the use of broad averages for assigning the cost of resources to cost objects and provides better measurement of the costs of overhead resources used by different cost objects. b. describes a costing approach that uses broad averages for assigning the cost of resources uniformly to cost objects when the individual products or services, in fact, use those resources in non-uniform ways. c. is a process used to categorize various activity cost pools on the basis of the different types of cost drivers, or cost-allocation bases, or different degrees of difficulty in determining cause-and-effect (or benefits-received) relationships. d. describes an event, task, or unit of work with a specified purpose. consistent with its more strategic focus, costing system refinement identifies activities in all functions of the value chain. costing system refinement first calculates the costs of individual activities and then assigns costs to cost objects such as products and services on the basis of the mix of activities needed to produce each product or service.