set intercept option

[Guest]

when selecting the set intercept checkbox in the trendline
option for a linear fit, the values for R^2 and slope are
adjusted automatically, i would like to understand how
those values are "re-calculated" any ideas?

 

[Tom Ogilvy]

Excel recalculates the formula used to determine the trendline. Since
changing the intercept option would change the slope of the trendline, the
slope must be recalculated. The R^2 value is dependent on the difference of
the trendline from the average value of Y, so changing the trendline would
require that this be recalculated as well.

If you mean what formula is used, you need to get a basic statistics book
and look at the linear regression and correlation - R^2 is the coefficient
of Determination.

Regards,
Tom Ogilvy

 

[Harlan Grove]

If you mean what formula is used, you need to get a basic statistics book
and look at the linear regression and correlation - R^2 is the coefficient
of Determination.

....

What, this wasn't drilled into you in some stats course?

R^2 = Sum((Estimated_Ys - Mean_Y)^2) / Sum((Actual_Ys - Mean_Y)^2)

But see

http://www.statisticalengineering.com/r-squared.htm