Understanding Correlations Among Spatial Processes

The Pearson product-moment, Spearman’s rank, point biserial and phi correlation coefficients are calculated to quantify the nature and degree of linear correspondence between observation pairs of attributes. Bivand (1980) and Griffith (1980) were among the very first spatial analysts to address the impacts of spatial autocorrelation (SA) on conventional Pearson correlation coefficients. In the decades since their studies, an increasing understanding has been attained about correlation coefficients computed with georeferenced data. This understanding includes how: SA alters conventional degrees of freedom and sample size, the nature and degree of SA affects correlation coefficients, and SA can simultaneously inflate and deflate correlation coefficients. The primary objective of this chapter is to review each of these topics, adding some extensions when possible.