5.2 Measuring of precision. Code precision is also estimated as the ratio of two frequencies. As with recall we calculate three values: 1) What code is it in? 2) What authority group is it in? 3) To what extent does its membership in the authority help predict what code it has? The numerator of the precision ratio is identical to the numerator of the recall ratio. As a proportion we compare it to the total number of spellings in the codes considered. Usually this latter value contains noise, i.e., name spellings brought together that are not part of the same authority group. Hence, precision is rarely one (100%).