The money quote of this article is: "I propose to term such correlations... the serial correlations for the given series." The basic idea here is that observa

The money quote of this article is: "I propose to term such correlations... the serial correlations for the given series." The basic idea here is that observations in a time-series are not actually independent because each observation is highly correlated with the previous observation, and so the usual significance tests and standard errors do not apply. Some links if you're interested in learning more about analyzing serial correlation and time-series data: http://en.wikipedia.org/wiki/Autoregressive_model http://en.wikipedia.org/wiki/Autoregressive_model http://en.wikipedia.org/wiki/Newey–West_estimator http://en.wikipedia.org/wiki/Newey–West_estimator http://en.wikipedia.org/wiki/Prais-Winsten_transformation http://en.wikipedia.org/wiki/Prais-Winsten_transformation