As we shall see in later chapters, the ability to predict how costs respond to changes in activity is critical for making decisions, controlling operations, and evaluating performance. Three major classifications of costs were discussed in this chapter—variable, fixed, and mixed. Mixed costs consist of variable and fixed elements and can be expressed in equation form as Y = a + bX, where X is the activity, Y is the cost, a is the fixed cost element, and b is the variable cost per unit of activity. Several methods can be used to estimate the fixed and variable cost components of a mixed cost using past records of cost and activity. If the relation between cost and activity appears to be linear based on a scatter graph plot, then the variable and fixed components of the mixed cost can be estimated using the quick-and-dirty method, the high-low method, or the least-squares regression method. The quick-and-dirty method is based on drawing a straight line and then using the slope and the intercept of the straight line to estimate the variable and fixed cost components of the mixed cost. The high-low method implicitly draws a straight line through the points of lowest activity and highest activity. In most situations, the least-squares regression method is preferred to both the quick-and-dirty and high-low methods. Computer software is widely available for using the least-squares regression method. These software applications provide a variety of useful statistics along with estimates of the intercept (fixed cost) and slope (variable cost per unit). Nevertheless, even when least-squares regression is used, the data should be plotted to confirm that the relationship is really a straight line. Managers use costs organized by behavior to help make many decisions. The contribution format income statement can aid decision making because it classifies costs by cost behavior (i.e., variable versus fixed) rather than by the functions of production, administration, and sales. In this chapter, the following learning objectives will be covered: In this chapter, the following learning objectives will be covered:

| | |Understand how fixed and variable costs behave and how to use them to predict costs. | |[pic] | |[pic] | |[pic] | | | |Use a scattergraph plot to diagnose cost behavior. | |[pic] | |[pic] | |[pic] | | | |Analyze a mixed cost using the high-low method. | |[pic] | |[pic] | |[pic] | |...