482 
15 
A 
Precision 
microns 
70 
5 
Diagram 3. Roof mean square values from grid points. 
-j Stereoscopic with approximate confidence interval 
— Monocu la r — 
— Binocular — —/<— —if— 
1: \J 2 between the precision of the stereoscopic and monocular 
method holds. Compute F = 2 • s 2 ste reo / s2 mono • When F 0 05 ^ F 
^ F o.95 you can state that the ratio holds on the 10 percent significance 
level. The F p -values are taken from a table of the F-distribution and 
with the degrees of freedom equaling 24 for both numerator and 
denominator. F 0>05 = 0.505, F 0.95 = 1-98. The computed F-values 
are shown in tables 5 and 6.