Cost estimation of software intensive projects: a survey of current practices

The authors describe a survey conducted at the Jet Propulsion Laboratory (JPL) to estimate software costs for software intensive projects in JPL´s technical divisions. Respondents to the survey described what techniques they use in estimating software costs and, in an experiment, each respondent estimated the size and cost of a specific piece of software described in a design document provided by the authors. It was found that the majority of the technical staff estimating software costs use informal analogy and high-level partitioning of requirements, and that no formal procedure exists for incorporating risk and uncertainty. The technical staff is significantly better at estimating effort than size. However, in both cases the variances are so large that there is a 30% probability that any one estimate can be more than 50% off