Correlogram

A correlation curve is a graphical representation of the autocorrelation of a time series. For this purpose, the correlation coefficients are plotted against the duration of the time difference. Exceeds ( falls below ) the upper limit (lower limit), then the null hypothesis that no autocorrelation exists, rejected with an error probability of:

T is the corresponding quantile of the t distribution, SE is the standard error. This is in this context usually based Bartlett's formula for MA ( l ) processes ( "moving average", see ARMA model ) is calculated:

In the picture above, therefore, the null hypothesis is rejected, that there is no autocorrelation between adjacent periods is. Observations of successive periods correlate significantly so. For other delays, the null hypothesis of missing autocorrelation, however, can not be rejected.