Sensitivity of field failure intensity to operational profile errors

Sensitivity of field failure intensity estimates to operational profile occurrence probability errors is investigated. This is an important issue in software reliability engineering, because these estimates enter into many development decisions. Sensitivity was computed for 59,200 sets of conditions, spread over a wide range. For 99.4% of these points, the failure intensity was very robust with respect to occurrence probability errors, the error in failure intensity being more than a factor of 5 smaller than the occurrence probability error. Thus projects do not have to spend extra effort to obtain high precision in measuring the operational profile, nor do they need to worry about moderate changes in system usage with time.<>