ti 
Jt 
  
However, these so essential functional relationships are in most cases not yet 
available to the planner, nor can they be readily established. Some of the reasons 
for this ares 
a) A lack of sufficient theoretical insight into the actual functional relation- 
ships 
b) A lack of sufficient statistical data needed to establish significant relatio 
ships 
c) The difficulty experienced in attempting to quantify or at least usefully 
classify many of the influencing factors. 
In order to make systematic planning possible, these dif ficulties must be removed. 
A comprehensive and systematic research effort will be required to this end. 
It would be of course unrealistic (and probably also not really necessary) to 
attempt to establish the exact functional relationships. Instead we have to 
establish useful approximations, based on reasonably realistic and accurate models 
  
of the actual relationships. 
The extent of allowable approximations will be governed by the objective and will 
fto 
ffer ‚according to the sensitivity of the desired results to the various required, 
relationships. (a Subject for Operational Research). 
Furthermore we will have to face the fact that certain relationships cannot be 
established with the desired accuracy. These will have to be considered in planning 
by applying stochastic models (estimating the range of uncertainty of input data) 
computing the resulting uncertainty of performance and cost models and considering 
ihis in the final decision). 
2.9 Establishment of cost models 
  
Cost models for alternative process components and sub-processes should represent 
the cost of their execution as a function of all those factors, which have a 
significant influence on them. 
With the help of these cost models, the planner can find out which combination of 
process components does not only yield the reguired product specifications but 
also represents the most efficient and economic total procedure. 
In general, cost models are primarily functions of 
a) basic cost factors, being unit costs for personnel, equipment material etc. 
  
and . 
  
b) production rates, being the required personnel time, equipment time, etc. fl 
certain production units. _ ; 
Both groups 
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