## Regression Formulas

The following formula are used for linear regression. In case of geometrical regression,
x and y have to be substituted by ln x and ln y. In case of exponential regression only y,
and in case of logarithmic regression only x has to be substituted.

### Formulas:

a = (Σy - b·Σx)/n
b = (n·Σxy - Σx·Σy)/(n·Σx^{2} - Σx·Σx)
Coeff. of determination r^{2} = h_{1}/h_{2}
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Coeff. of correlation r = √r^{2}
Variance s^{2} = (h_{2} - h_{1})/(n-2)
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Standard deviation s = √s^{2}
with h_{1} = b·(Σxy - 1/n·Σx·Σy) and h_{2} = Σy^{2} - 1/n·Σy·Σy