where: 4 is the regression coefficient, B. is the parent of the regression, 
5, and s, are the sample s.d. of the variable x and y respectively and r 
is the coefficient of correlation between x and y. It is shown that 7 — 
value is distributed in Student’s form with n — 2 degrees of freedom [4]. 
The computation has given the result: #— 0,097 with 23 d. of fe. The 
correlation and regression are no significants. 
4. 
At the end of the researches carried out, considering the linear depen- 
dence between total errors of ground control and total plotting accuracy 
we have at last grupped the data according to the different plotting ope- 
rators with the purpose of obtaining some general qualitative informa- 
tion on the human influence on plotting works when the ground control 
points coordinates are altered. 
The subject of this last stage of the researches has been always the obser- 
vations collected in columns 4 and 11 of Table I and it has required 
the determination, for each operator, of the arithmetic mean of the errors 
of the variances, of the standard deviations, of the linear correlation 
coefficients between the two considered variables and of their 7-Student 
distributions. 
The numerical values obtained by this last research on small samples, 
have been listed, in comparison with the operator's age and with his 
years of experience, in Table IV. 
  
  
  
  
  
  
  
  
  
TABLE IV 
Operator A B C D E 
Age 24 | 45 33 40 55 
Years of experience | ^8 5 5 13 25 
| 
| 
Arithmetic mean of the 
ground control total errors 0,78 0,83 0,86 | 0,86 0,82 
Variance 0,0217 0,0098 0,0394 0,0275 0,1174 
Standard deviation 0.15 0,10 0,19 0,17 0,34 
Arithmetic mean of the 
photogrammetric plotting 
total accuracy 0,34 0,32 0.33 0,25 0,27 
Variance 0,0019 0,0009 0,0027 0,0004 0,0071 
Standard deviation 0,04 0,03 0,05 0,02 0,08 
Coefficient of correlation 
between ground control 
error and plotting accuracy 0,072 0,735 -0,091 —0,769 0,151 
Distribution /-Student | 0,124 1,878 0,157 2,088 0,264 
|