ENClM-fiRIXG I'ROIU.F.MS ()/• 77//-; /(/:/./. SYSITM S2\ 



These engineering cost comparisons may be considered as composed 

 of four parts or operations; namely, the promises or known factors and 

 assumptions; the formulation or set-up of the problem ; the solution 

 or mathematical calculations and tinalK- the interpretation of the 

 results. The determination of the premises and formulation ai a 

 i;iven problem is, of course, a matter specific to that problem, and here 

 the engineer nmst exercise sound judgment, for unless the assumptions 

 upon which the work is based are reliable the study itself is of little 

 value. The mathematical calculations arc, of course, a definite thing. 

 However, the interpretation of the results must always be a matter 

 of engineering judgment anil full weight must be given to those factors 

 which by their nature cannot be evaluated in the cost comparison. 



A cost study is a fundamentally important tool in assisting the 

 engineer to reach a decision as to the most desirable plan or program, 

 but as indicated it cannot be used to replace the exercise of judgment 

 on his part. The solution of an engineering problem is, in general, 

 not a matter that can be demonstrated mathematically as can, for 

 example, the proposition, that the square of the hypotenuse of a right 

 triangle is equal to the sum of the square of the two sides. An en- 

 gineering study rather requires in addition to all of the definite facts 

 that can be brought to bear on the question the exercise of sound 

 judgment on the part of the engineer in weighing the results of the 

 cost study with all related business or other factors bearing on the 

 problem. 



Some factors involved in these engineering studies are often of a 

 character which do not permit of expression as a direct charge against 

 a given plan, but must be considered on a broader basis such as the 

 difference in quality or dependability of the service, etc. Also it is 

 important to keep in mind, for example, that, other things being 

 equal, a plan requiring large investments has disadvantages as com- 

 pared with one requiring a smaller investment so that even though the 

 plan involving a larger investment may prove in from the cost study 

 by a small margin, it may be desirable to adopt the alternative plan 

 so as to avoid tying up considerable amounts of fixed capital. Another 

 question to be kept in mind in interpreting cost studies is whether the 

 more expensive type of plant, usually a higher type of plant, can be 

 adopted satisfactorily at a later date or whether the decision to be 

 made at the present time precludes its adoption later. In the former 

 case it is often wise to go further in deferring fixed capital expenditures 

 than in the latter case. F"inall>', throughout all of his work the en- 

 gineer must have foremost in his mind the fact that the telephone .sys- 

 tem exists for the purpose of furnishing service to the public and the 



