The root mean square error (RMS Error), or root mean square deviation, is a measure of the differences between predicted values and observed values.
where
Hint
Similar to variance, RMS error use the mean of the squared residuals. Using just the mean of the residuals in linear regression would always result in zero.
Given data of size 2, where the 2 values have residuals of 9 and 6, what is the population RMS error?
RMS Error in Linear Regression
In linear regression, a quick formula to calculate the RMS Error is
where
We can see that with perfect correlation (i.e.