Sum- test 
FIG | — DISTRIBUTION OF POINTS 
2. The correlation between the two basic tests is rather weak; e. g. 
those 10 % in each test having the lowest number of points are only 
the same in 3.9 96 of the cases of the total number of tested persons. If 
complete correlation was a fact it should be 10 96. Those 14 persons 
having 0 or 1 point in the stereoscope-test had 4.4 points as an average 
in the polaroid-test and those 19 persons having O or 1 point in the 
polaroid-test had 3 points as an average in the stereoscope-test. This is 
caused by the various "bugs" in the methods and shows that one should 
not rely upon.only one of the two methods. 
3. A repeated test after some training increases the number of points 
but this may be caused by several psychological factors and may not 
represent a real increase in stereo vision quality. Those having had 
some experience in stereo-interpretation before the test show a slightly 
better result than those without previous training. 
4. Those, being one-eved were 0,44 96 and those having O or 1 
point in both tests were 0,62 96. Consequently 1,1 % had no stereo- 
vision at all. About 3 96 more show rather bad results but the distribu- 
tion curve, which may be regarded as a quality-guide, is not raising 
clearly until the 10 less good percents are passed. 
5. Quite interesting is that increasing age up to 40—49 years shows 
an increase in the results. This is demonstrated in Figure 2 where the 
broken curves indicate the standard deviation in each age-group. 
6. No significant difference in the results have been found when 
comparing the two sexes and the educational level. 
7. The types of work seem to have a certain influence directly or 
indirectly. The best results come from foresters and surveyors. Draft- 
ing personnel comes thereafter closely followed by military personnel. 
4