Enhancing the Jacquez k nearest neighbor test for space-time interaction

The Jacquez k nearest neighbor test, originally developed to improve upon shortcomings of existing tests for space-time interaction, has been shown to be a robust and powerful method of detecting interaction. Despite its flexibility and power, however, the test has three main shortcomings: (i) it discards important information regarding the spatial and temporal scales at which the detected interaction takes place; (ii) the results of the test have not been visualized; and (iii) recent research demonstrates the test to be susceptible to population shift bias. This study presents enhancements to the Jacquez k nearest neighbors test with the goal of addressing each of these three shortcomings and of improving the utility of the test. Data on Burkitt's lymphoma cases in Uganda between 1961 and 1975 are used to illustrate the modifications and enhanced visual output of the test. Output from the enhanced test is compared with that provided by alternative tests of space-time interaction. Results show the enhancements presented in this study transform the Jacquez test into a complete, descriptive, and informative metric that can be used as a stand-alone measure of global space-time interaction.