The statistics that are used in describing the spatial distribution of crime incidents are explained and illustrated with examples from CrimeStat III.
The crime incident data used are from Baltimore County and Baltimore City. A figure shows the user interface for the spatial distribution statistics in CrimeStat IV. For each of these, the statistics are first presented, followed by examples of their use in crime analysis. The most basic type of descriptors for the spatial distribution of crime incidents are called "centrographic statistics." These are indices that estimate basic parameters about the distribution. These indices are discussed as the mean center, median center, center of minimum distance, standard deviation of X and Y coordinates, standard distance deviation, and standard deviational ellipse. Also discussed are the uses of the geometric mean, harmonic mean, and average density. Regarding the output files, the chapter explains calculation of the statistics, tabular output, and graphical objects. How to use the outputs of the routines without formal testing is also discussed. This is followed by examples of centrographic statistics that include June and July auto thefts in Baltimore's precinct 11, as well as serial burglaries in Baltimore City and Baltimore County. Issues in directional mean and variance are discussed, followed by a discussion of the uses and limitations of the "convex hull." Extensive figures with computer screens, 21 references, and 2 attachments that pertain to routes used by motor vehicle thieves and centrographic analysis