The Average Fault Group Size metric, which appears in the Fault Group Size Percentages section of the Fault Isolation Report, represents the average number of replaceable items in fault groups isolated by the diagnostic sequence within the current diagnostic study. This Test limit is not probability-weighted and therefore does not reflect the expected size of the fault groups that would be isolated in a fielded system. (Note: The calculation of this metric is dependent upon the selected Fault Group Counting Method.)
Calculation
This Test limit can be calculated by adding up the sizes of all isolated fault groups and then dividing the sum by the total number of isolated fault groups:
Alternatively, this Test limit can be calculated by summing the products of the Test limits in fault group Size and % columns (under the Isolation Percentages Using Testing Only label) for each row in the Fault Group Size Statistics table. To simplify the equation (shown below), this can be calculated using all sizes up to and including the maximum isolated fault group size:
