Statistical analysis is often used to explore your data—for example, to examine the distribution of values for a particular attribute or to spot outliers (extreme high or low values). Having this information is useful when defining classes and ranges on a map, when reclassifying data, or when looking for data errors.In the example below, statistics have been calculated for the distribution of senior citizens by census tract in this region (percentage age 65 and over in each tract), including the mean and standard deviation, as well as a histogram showing the distribution of values. Most tracts have a lower percentage of seniors than the mean, but a few tracts have a very high percentage.
