AuthorsS. Grimstad and M. Jørgensen
TitleInconsistency in Expert Judgment-Based Estimates of Software Development Effort
AfilliationSoftware Engineering, Software Engineering
Publication TypeJournal Article
Year of Publication2007
JournalJournal of Systems and Software

Effort estimation of software development work is partly based on non-mechanical and unconscious processes, i.e., human judgment. For this reason, a certain degree of intra-person inconsistency is expected, i.e., the same information presented to the same individual at different occasions may lead to different effort estimates. In this paper, we report from an experiment where seven experienced software professionals estimated the same sixty software development tasks over a period of three months. Six of the tasks were estimated twice. We found a high degree of inconsistency in a subject's effort estimates of the same task. The mean difference of the effort estimates of the same task by the same estimator was as much as 71%! Surprisingly, the software professionals' estimation accuracy on previously completed development tasks did not correlate with their degree of estimation inconsistency in the experiment. We discuss reasons for and consequences of our findings.