Our goal is to develop models that will predict quality factors related to faults for each module. If one supplies values for the independent variables, then one can calculate the value of the dependent variable. A software quality model has independent variables that may be measured earlier in the life cycle than the dependent variable, quality. Thus, the calculated dependent variable value is a prediction of what one expects its measured value to be. A variable such as the number of faults is the dependent variable that we want to predict.
Total faults are directly measurable only after software has become operational.
In contrast, software product metrics and process metrics can be measured during development. A suitable software quality model can make predictions when it is not too late to take economical compensatory actions. We develop models based on data from a completed past project where the quality factor is available for each module. Then the model is ready to apply to a current similar project, using only software metrics to make a quality prediction for each module. With predictions in hand, a project can adapt the development process so that product reliability is improved.