PopuljlO 



TABLE 2 



Accuracy and range of coimts from samples fitting Poisson Distribution. 



Count 

 X 



1 



U 



9 



16 



25 



36 

 U9 

 6U 



81 

 100 

 121 

 Ihh 

 16? 

 195 

 225 



500 



1000 



standard Error 



s/r 



1 



2 



3 



k 



5 



6 



7 



8 



9 



10 



11 



12 



13 



lU 



15 



22 

 32 



SE ^ Count 

 n/Tx 100 



100 

 50 

 33 

 25 



20 

 17 

 lU 

 13 

 11 

 10 

 9 



-"- The Poisson Distribution is asymmetrical but becomes more nearly sym- 

 metrical as values increase, so that twice the Standard Error may be 

 taken as the 95^ fiducial limits, as in the Normal Distribution for 

 counts of 9 upwards. 



TABLE 3 



CUdnces of detecting eelworms in soil 



"low" population levels (lOOg. samples) 

 Equivalent concentration; 



Expected 

 count per 

 sample 

 lOOg . 



0.01 



Percentage changes ; 

 Of finding one Of failing to 

 or more cysts find cysts 

 Detection Failure 



1 

 10 



50 

 63 

 85 

 95 

 98 

 99 

 99,9 



99 

 90 

 30 

 37 

 15 



5 



2 



1 



0. 



1000 tonr; or 10>'f';. of top noil P'^r aero. 



