The COSMIC Functional Size Measurement Method Version 3.0.1 Guideline for assuring the accuracy of measurements

G Gu ui id de el li in ne e f fo or r a as ss su ur ri in ng g t th he e a ac cc cu ur ra ac cy y o of f m me ea as su ur re em me en nt ts s A Ac ck kn no ow wl le ed dg ge em me en nt ts s of this material is granted provided that the copies are not made or distributed for commercial advantage and that the title of the publication, its version number, and its date are cited and notice is given that copying is by permission of the Common Software Measurement International Consortium (COSMIC). To copy otherwise requires specific permission. A public domain version of the COSMIC documentation and other technical reports, including translations into other languages can be found on the Web at www.cosmicon.com. Purpose of the Guideline This Guideline provides an overview of the factors that influence the quality of a functional size measurement, particularly a COSMIC size measurement, and advises how to organize the measurement process so as to obtain accurate size measurements and/or to improve measurement accuracy. Quality assurance actions aim to improve quality and to help achieve desired quality levels. In our case a measurer's quality aim will be to achieve a desired measurement accuracy level. The desired accuracy of a measurement (see below for the definition of 'accuracy') will probably vary with the project circumstances. Early in the life of a new software project, only an approximate estimate of size may be possible, but it may still be of acceptable accuracy. At the other extreme, e.g. in the context of outsourced software contracts where a measurement may at some time become a matter of legal dispute, highly accurate measurements are likely to be essential. In order to assure the desired accuracy of measurements, it is important to have both well-trained and experienced measurers and an adequate and repeatable measurement process. Audits are also necessary to check and to assure ongoing accuracy. In managing the measurement process, two main quality control efforts are essential. They are, in order of importance: • Error-prevention, • Defect-detection. Error-prevention efforts concern three main factors 1 , namely assuring the: • Quality of the measurer(s) • Quality of the software artifacts • Quality of the measurement process Defect-detection that only identifies defects may not help much …