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 z  y   y 2
y
  (4.31)
y
n ,

— correlation ratio;
z z
x , y — frequency of row distribution of x, y;
y
— arithmetic mean value of y;
y
x — conditional average y for the corresponding
classes of row distribution x.
If characteristics in empirical formula are linear, it's best
to use method of least squares. This means that characteristics
are determined when the sum of squared deviations of measured
values of functions y from its calculated values is minimal.
The regression equation is:
Y(х) = а + b∙х
Values of characteristics a and b are determined by the
formulas:
 n  x  y   x   y
b  i i i i
2 2 (4.32)
 n  x  (  x )
i i
,

 y  b  x
a  i i (4.33)
n ,
where n — number of pairs of x, y obtained in experiment.
Task 4.10
Determine coefficient of correlation for curve of elasticity
of isobutane vapor, if :
°
Temperature C 273 283 303 323 343 413 453
Pressure, MPa 0.15 0.25 0.4 0.75 1 2 8

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