The selection of the most efficient sampling method should not be based 
only on the standard deviai;on figures. It will also be necessary to 
calculate the number of plots for a required standard error per cent and 
to determine the number of ;an-days, in office and field, included in the 
total activities of each meth: 
If the standard error percenta;. is assumed to be S-% 5, the number of 
plots for the sampling methods then are v 
calculated for: 
; ; 37.08? 
unrestricted sampling: n - 2.7 55, 
5 
27 98° 
stratified sampling n = TERQUE = 3S1 (of which 25 in stratum dense 
5 and 6 in stratum open) 
26 93? 
For the two-stage PPS sampling the number of PU's is m - eT - 29. 
5 
As sampling is done here with replacement, the actual number is reduced 
to m = 23. 
This means that the number of secondary units (SU) is 23 x 2 = 46. 
2 
63.72 
For the two-phase sampling n, = SEES = 163. These, however, are photo 
5 
plots and in order to know how many of them are required for field 
enumeration, the optimum ratio field/photo plots should be calculated. 
Assuming a cost ratio of photo/field plots: Vu = 1/60, and from 
the total cost: C - nee, * E and from the variance as well 
  
  
Dean 2 2 
^n "n By c 
y = n f + = c 
f 
p n, 
x s? 
2| n v.C “p 
the following ratio is derived:| n /n 00m P 
p fo 2 - 2 
p.c S c 
n c f 
  
  
    
    
   
   
    
   
  
   
   
   
      
   
   
     
   
  
  
  
  
  
    
    
   
   
or I 
So foi 
In Tal 
sampl: 
Table 
  
Samy 
meth 
  
Unre 
Strat 
Two- 
Two- 
  
  
Table 
field 
in ea 
on foc 
easily 
distai 
sheet: 
bound: 
summa 
calcu: 
For ci 
calipe 
trees 
numbe: 
10,00( 
or PU 
(= 56- 
The d: 
plots 
hours 
calcu. 
The sj