- 8 - 
Table 3. Standard error of unit weight (mm). 
Picture 
3 
Root 
mean 
square 
Degrees of 
freedom 
Aper 
ture 
Picture 
1 
Picture 
2 
f: 5. 6 
0. 0049 
0. 0056 
f : 8 
0. 0051 
0. 0054 
f : 11 
0. 0060 
0. 0052 
f: 16 
0.0028 
0.0033 
Root 
mean 
square 
0. 0046 
0.0050 
359 
0.0048 
0. 0051 
359 
0.0061 
0.0058 
3 59 
0.0036 
0.0032 
353 
0.0049 
1430