SEMAINE D'ÉTUDE SUR LE ROLE DE L’ ANALYSE ECONOMETRIOUE ETC. 
29 
The resulting estimate can then be used for the inferences (43 
and (44). 
Next we come to Fig. 4b, which illustrates a demand rela 
tion specified bv wav € an 2 “her predictor, sav 
(46) 
wilh 
(47 
A 
where a 1s the demand elasticity with respect to price. A typical 
inference from the model (46)-(47) is that if price is known, 
say p,, the expected value of consumer demand is given by 
(48) 
Gi 
Comparing with (43) and (44) we note that the present inference 
is attenuated in two respects: 
1) Whereas the inference (43) is deterministic, exact, the in- 
ference (48) about consumer demand is designed to be true 
only as an expected or average value. This is so because 
demand is influenced by many other factors than price, 
influences that are summed up in the residual variable vu. 
Whereas the deterministic relation (42) allows the twofold 
inference (43)-(44), the stochastic model (46)-(47) allows 
only the prediction (48) of d for known p. In fact, if we 
solve (48) for p, and drop the subscript the ensuing relation 
> 
JU, 
is not an eo ipso predictor 
E(pld) Zc « 
Wold - pag. 25