Cross Correlation and Prewhitening

I am using cross correlation to demonstrate a potential link between two time series (ext & co). Both series are strongly autocorrelated, so it is difficult to assess the dependence between the two series. For a quick preliminary analysis, the cross correlation shows a clear (somehow delayed) link between the two time series, although it might spurious. . Prewhitening seems to be the best option; I will prewhiten my x variable by fitting an ARIMA process and then use the coefficients to filter my variable y. My question is if I should estimate the coefficients of the ARIMA process (for example using auto.arima) using my series x or by using the residuals of the OLS regression of x on y.

• If you are primarily interested in a link between two time series (and not their transformations), will you be answering the right question if you use prewhitened data?.. Jan 13 '16 at 20:23
• Yes the right question is being answered though a single filter pre-whitening operation (not two filters !) . See onlinecourses.science.psu.edu/stat510/node/75 for a basic ( largely correct) primer on this approach. Note that the single filter does not distort but amplifies any predictive relationship between the two original series. Jan 13 '16 at 22:45
• Not quite. If two series share a common trend (stochastic or deterministic) and this trend is removed by prewhitening, you will entirely miss the obvious connection between the series. Apr 16 '16 at 14:11