Figure 3.2. Lagged scatterplots of tree-ring series MEAF. These are scatterplots of the
series in Figure 3.1 with itself offset by 1, 2, 3 and 4 years. Annotated above a plot is the
correlation coefficient, the sample size, and the threshold level of correlation needed to
reject the null hypothesis of zero population correlation with 95 percent significance
(α=0.05). The threshold is exceeded at lags 1, 2, and 4, but not at lag 3. At an offset of 3
years, the juxtaposition of high-growth 1999 with low-growth 2002 exerts high influence
(point in red rectangle).