# Is it Possible to Disregard Obsolete Requirements? - An Initial Experiment on a Potentially New Bias in Software Effort Estimation

## TL;DR

This study investigates whether obsolete requirements influence software effort estimation, revealing that explicitly instructing to disregard certain requirements paradoxically leads to higher effort estimates, highlighting a potential bias in estimation practices.

## Contribution

It provides the first empirical evidence of a bias caused by obsolete requirements in effort estimation, suggesting the need to consider this factor in estimation accuracy.

## Key findings

- Explicit instructions to disregard requirements increase effort estimates.
- Obsolete requirements may introduce a bias in effort estimation.
- Psychological explanations for the bias are proposed.

## Abstract

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.