  Effort estimation is a complex area in decision-making, and is influenced by
a diversity of factors that could increase the estimation error. The effects on
effort estimation accuracy of having obsolete requirements in specifications
have not yet been studied. This study aims at filling that gap. A total of 150
students were asked to provide effort estimates for different amounts of
requirements, and one group was explicitly told to disregard some of the given
requirements. The results show that even the extra text instructing
participants to exclude requirements in the estimation task, had the subjects
give higher estimates. The effect of having obsolete requirements in
requirements specifications and backlogs in software effort estimation is not
taken into account enough today, and this study provides empirical evidence
that it possibly should. We also suggest different psychological explanations
to the found effect.
