  Background: Agile software development has become a popular way of developing
software. Scrum is the most frequently used agile framework, but it is often
reported to be adapted in practice. Objective: Thus, we aim to understand how
Scrum is adapted in different contexts and what are the reasons for these
changes. Method: Using a structured interview guideline, we interviewed ten
German companies about their concrete usage of Scrum and analysed the results
qualitatively. Results: All companies vary Scrum in some way. The least
variations are in the Sprint length, events, team size and requirements
engineering. Many users varied the roles, effort estimations and quality
assurance. Conclusions: Many variations constitute a substantial deviation from
Scrum as initially proposed. For some of these variations, there are good
reasons. Sometimes, however, the variations are a result of a previous
non-agile, hierarchical organisation.
