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

This paper deseribes a survey conducted of the staff of the Jet Propulsion Laboratory (JPL) who estimate software costs for software intensive projects in JPL’s teehnical divisions. Respondents to the survey deseribed what techniques they use in estimation of software costs and, in an experiment, each respondent estimated the size and cost of a speeiflc 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 siztx however, in both cases the variances are so large that there is a 30 pereent probability that any one estimate can be more than 50 percent off. 1