This document describes a mathematical model designed to produce a weighted, standardized index that can be used to represent a statistically unbiased measure of a Future Farmers of America (FFA) chapter's level of activity in relation to other chapters in Ohio. The index, called the FFA Chapter Activity Index, is expected to be applicable to other states as well. The case for the new model is that the self-report instruments that have previously been used to collect data about the activity level of a chapter often produce biased or inaccurate information. The paper explains the model components and specifically how to compute the index by (1) calculating a weighted coefficient equal to the number of FFA members in the chapter divided by the number of instructors in the agricultural education department; (2) calculating a standardized score that represents the chapter members' state degree and district proficiency awards; (3) calculating a standardized score that represents the chapter's placing in the various agricultural skills contests; (4) calculating a standardized score that represents the chapter's participation in the various chapter awards programs; and (5) summing the three standardized scores and multiplying the result by the weighting coefficient. The mathematical model eliminates the reliability concerns raised by the older instruments; for example, if the same set of data is substituted into the model several times it always produces the same result. Good content validity as rated by a panel of experts is indicated. Two examples are given to explain the index, and the advantages of the index compared to the more common self-report method of assessing chapters' activities are discussed. Recommendations and six references conclude the document. (CML)