In a time series with OLS regression curve Y-hat (rolling linear regression), and with n=20, what can I say about this transformation? This formula is similar to a differential dY/dt minus an integral of a data series. 
The first term is the n-th residual of the OLS model. The second term is closely related to the SSE or MSE functions. However, I have summed the raw residuals without squaring so this is basically a term that follows the trend in the residuals.
- What is the variance of each term? (1)
- Can I use SSE or MSE to find (1)?
- Does anybody recognize this kind of data transform? Related literature or topics? (3)
P.S. The "1/4" in the second term is really just 5/n for my formula.
Thanks!