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area, however, should then be made (see page 8). The volumes and standard 
deviations of Table 2 are each calculated as the mean of 35 samples 
(indicated by a weight 35). Means of 35 samples are calculated, in order 
to have more reliable estimated means for comparison (Table 2). The 
values moreover permit an estimate of the coefficient of variation of 
the standard deviation (CVs), column 7, Table 2. 
  
  
  
  
Table 2 
Estimates of volumes and standard deviations resulting from a two stage 
PPS sampling with M differ: t PU areas per grid cell and different 
number of SU's/PU. PU-variab: : conifer area. 
PU number | total standard deviation CVs weight = 
grid of | volume number 
Size SU’s/PU of 
3 3 samples 
M ha m m % % 
2 1,941,234 484,871.2 25.0 10.8 35 
62 225 5 1,938,461 343,157.1 17.7 8.2 35 
10 1,930,048 286,801.8 14.9 6.3 35 
15 1,923,763 265,972.4 13.8 4.0 35 
2 1,962,159 480,226.8 24.5 12.4 35 
5 1,930,456 333,115.9 17.3 13.7 35 
10 1,928,864 262,413.7 13.6 10.3 35 
34| 450 | 15 1,928,456 251,250.4 13.0 9.4 35 
20 1,916,948 264,684.3 13.8 4.4 35 
25 1,930,696 230,647.8 12.0 3.8 35 
30 1,945,130 206,714.0 10.6 2.8 35 
35 1,942,483 221,429.8 11.4 2.9 35 
2 1,898,175 476,692.1 25.1 13.6 35 
5 1,932,550 326,208.1 16.9 14.7 35 
10 1,931,861 284,195.7 14.7 11.9 35 
29 675 15 1,931,113 243,176.0 12.6 12.4 35 
20 1,929,870 230,200.2 11.9 10.1 35 
25 1,929,021 218,799.1 11.3 9.1 35 
30 1,934,078 211,262.9 10.9 7.8 35 
35 1,927,594 207,221.2 10.8 7.4 35 
  
  
  
  
  
  
  
  
  
  
The conifer volumes (Tables 1 and 2) do not differ significantly, which is 
in accordance with the nature of the volume Formulae 2 and 4. Total forest 
area as a variabie for the PU (Table 1) gives a larger area, a lower mean 
volume, but the same total volume. SU's falling in non-conifer area have 
zero volumes. Table 2 also demonstrates that an increase in the number of 
SU's/PU results in a decrease of the standard deviation (columns 5 and 6). 
This is explained by the within PU-varíance term, similar to that in 
Formula 1, which reduces with an increase in n. An increase of the size 
of the grid cell, which gives a larger range of the PU areas does not 
result in a reduction in the standard deviation.