equals —1 or 1, all points on the correlation diagram are on a line. The further the value of r is from
—1 and 1, the less the points are massing about the line and the less reliable is the correlation. If r is more
than 0, it shows a positive correlation (Y is in proportion to X) and if r is less than 0, it is a negative
correlation (Y is in inverse proportion to X).
The equation for the straight line is Y = a + bX. The point at which the line crosses the Y axis is a. The slope
is b.
r
a
b
Correlation coefficient
$xy
r =
Vs.
'xx ' ^yy
a = y — bx
Coefficient of linear
regression equation Y = a + bx
§xx
Syy = S /
sxy = Z x y
\
(S x )2 >
n
(Xy)2
n
Xx-Xy
n )
53
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