::: HARRIS. KIRKPATRICK, BLAKESLEE. WARXER AND CARD 



mine which formula gives the lowest delation. Two methods may be 

 suggested. 



First, the deviations may be summed without regard to sign and divided 

 by their number. This gives an avtiage. deviation without regard to sign 

 of the UMrikted tram the maided production for any flock and period 



The disadvantages of this method are two: (a^ It ignores mathematical 

 convention with regard to signs, (b) It gives large and small deviations 

 a weight proportional to their actual magnitudes. Thus 50 deviations of 

 3 eggs each and 50 deviations of 5 eggs each would give an average devi 

 ation of 4 eggs, while 50 deviations of 1 egg each, 25 deviations of 6 eggs 

 each and 25 deviations of 8 eggs each would also give a general average 

 deviation of 4 eggs. But since one of the ideals to be attained in the selec 

 tion of a formula would seem to be to obtain one which will avoid the 

 giuuet errors it seems proper to weight the larger deviations. This can 

 * **** inMii f*p*r fi tjiiariint Then 



For completeness we shall employ all three methods in the tests of equif 

 tions used in this paper. 



The method of taking the difference has been so chosen that a positive 

 sign, indicating larger error of estimating, shows an inferiority in the 

 equation. 



Two of the criteria are values without sign. In the case of the average 

 deviation with regard to sign the *&amp;gt;* S may be either positive or negative. 

 Xa comparing taw &amp;lt;lM*ioi methods of prediction we have considered that 

 the magnitude of the error and not the sign n the critical point In such 

 comparisons, thru fan., aft of the ** have beam considered as alike in 

 sign. Cases may pnaHJily arise in which it is fWM&amp;gt; to consider the 

 question of over prediction or under prediction by two formulae which 

 may be under consideration. If so our tables of criteria and not the difer- 

 enots aa pnbnthed ahonU be consulted by the lender. 



characteristic equation given above is strictly valid only when 

 to the population from which it is deduced. Its extension without 

 modification to another population is justified only if the physical cons 



