October 14th, 2009, 4:55 pm
QuoteOriginally posted by: doubleslitSo if I'm looking at a price to sales ratio series against market returns, do I need to difference the price to sales ratio series first before I do correlation analysis? Or should I explore cointegration between the price to sales ratio series with the market's closing prices?it depends. i'd test for cointegration, look at johanssen (whatever the spelling is) test. if there's a reason to believe in cointegration, then do it. otherwise, diff would be an option. i dont think there's one easy rule to decide.