I am trying to validate the use of a model. I have two streams of NPV calculations, one is the actual return, the other is the projected return. Those streams are turned into deltas from one time period (1 day) to the next to create it's own time series (net from day-to-day)
The current model uses a regression approach to compare the delta results. The comparison is done in Excel with the LINEST formula. I am concerned with that approach because LINEST expects known X and known Y values. But if I am being given two streams, aren't those two Y values? The X values are still unknown and I don't think LINEST would apply in this scenario.
What other approaches can be used to compare two sources of return data?