-5 The analysis of the data obtained and the development of relationships between product durability and those factors which impact upon it were found to be within the scope of traditionally employed statistical methodologies. However, the use of these methodologies is expected to be restricted over the short-run because of various problems associated with the available data base. These problems are of the following form: a. Most of the available data are qualitative rather than quantitative. b. The available quantitative data cover only a limited C. time span. The conditions under which a specific product was for comparison purposes across the product category. duct does not necessarily reflect its true useful e. Maintenance records, repair records and associated costs are not usually available for most products. The form and nature of currently available data are discussed next. An analytical treatment, illustrating the use of various statistical techniques, is also presented. -6 2.1 Data Acquisition As stated above, data were not available for all of the study product categories and, of those which were available, not all were quantitative in nature. The form also varied, ranging from information which clearly qualified the existing data (e.g., for construction equipment) to that which is collected on an intermittent basis as part of consumer surveys, and is therefore of inferential value. These data characteristics (nature and form) are described for the following product categories 2.1.1 Heavy Construction Equipment Of all the product categories studied, we found that * This period is not necessarily equivalent to physical life. -7 Track-Type Pipelayers Wheel Tractor Off Highway Trucks What! Type Wheel Loaders Track Type Motor Graders TABLE 2. GUIDE FOR SELECTING DEPRECIATION PERIOD BASED ON Source: Caterpillar Tractor Co. 23-615 073 11 -8 i.e., motor graders, is shown in Figure 1. The com- A summary of average physical life, for various major sentative. 2.1.2 Tires There are several variables which have a marked effect |