28 
T,, Z. 
Oe 4p) 
Figure 11. An iterative method for determining a 7 associated with a given 7 
T = T. with line of regression. This gives 4,. From equation 
(9), we have 
Second, this point has the coordinates (2. ; Z,)- In the new coordi- 
nate system, it has coordinates (7',,0), where 7’, can be 
computed by substituting 7, and 7, into equation lla. Pass the 
line 7'=T', until it intersects the interpolation curve at b. This 
point has coordinates (n= IP ,2', ), where 2’, is computed from 
equation (12) by putting 7 for 7'. Next, through (7',,7Z',); 
pass a line parallel to 7 axis until it intersects line 7 = TZ, at the 
