This booklet is a programmed self-instructional guide for the computation of arithmetic mean. Developed to serve the needs of public health professionals, it is not an exhaustive or technical treatment of statistics. It is limited, first, to descriptive statistics (tables, graphs, descriptive ratios, measures of central tendency, and measures of dispersion) and, second, to those concepts and techniques most needed by health professionals working routinely with basic statistical data. Intended primarily for public health nurses and sanitarians with a college degree or its equivalent, the guide is designed to be used when the need to compute and use the arithmetic mean arises. Several computational procedures for finding the arithmetic mean are provided, each with accompanying step-by-step examples. These include procedures for: ungrouped, discrete data; ungrouped continuous data; grouped (single value), discrete data; grouped (interval), discrete data; grouped (single value), continuous data; grouped (interval), continuous data (rounded); and grouped (interval), continuous data (non-rounded). Also presented is a condensed, simplified reference to selecting the correct computational procedure when the proper procedure to use is not known. (BL)