Calibration Results of COCOMO II . 1997

COCOMO II is an effort to update software cost estimation models, such as the 1981 COnstructive COst MOdel and its 1987 Ada COCOMO update. Both these and other 1980’s cost models have experienced difficulties in estimating software projects of the 90s due to new practices such as non-sequential and rapid-development process models; reuse-driven approaches involving commercial-off-the-shelf (COTS) packages, reengineering, applications composition, and application generation capabilities; objectoriented approaches supported by distributed middleware; software process maturity effects and process-driven quality estimation. The COCOMO II research effort has developed new functional forms reflecting these practices, and is concentrated on developing a model well-suited for the 1990s and then annually updating it for the forthcoming years of the 21 Century. The current COCOMO II.1997 has been calibrated to a dataset of 83 projects from a mix of Commercial, Aerospace, Government, and FFRDC organizations. The estimates of the 1997 calibrated model are within 30% of the actuals 52% of the times before stratification by organization; and within 30% of the actuals 64% of the times after stratification by organization. The 1997 calibration results indicated that the following changes from COCOMO ’81 to COCOMO II were successfully explaining sources of variation in the project data : • Replacing the COCOMO ’81 Development Modes by the 5 exponent drivers Precedentedness, Development Flexibility, Architecture/Risk Resolution, Team Cohesiveness, and CMM-based Process Maturity. • Adding multiplicative cost drivers for Amount of Documentation and Multisite Development.