I did (sort of) read the whole thing and it did not indicate how much time the non-TDD teams spent fixing their higher defect count. Did they take more time than the equivalent 15%-35% increase in dev for the TDD teams? Perhaps it was a wash? I don't know.
How accurate is to compare the various project teams? It always seems to me that no two projects and no two dev teams are ever the same. How do you account for the differences? The researcher somewhat addresses this but I am not fully convinced:
>>"...The projects developed using TDD might have been easier to develop, as there can never be an accurate equal comparison between two projects except in a controlled case study. In our case studies, we alleviated this concern to some degree by the fact that these systems were compared within the same organization (with the same higher-level manager and subculture).Therefore, the complexity of the TDD and non-TDD projects are comparable..."
How accurate is to compare the various project teams? It always seems to me that no two projects and no two dev teams are ever the same. How do you account for the differences? The researcher somewhat addresses this but I am not fully convinced:
>>"...The projects developed using TDD might have been easier to develop, as there can never be an accurate equal comparison between two projects except in a controlled case study. In our case studies, we alleviated this concern to some degree by the fact that these systems were compared within the same organization (with the same higher-level manager and subculture).Therefore, the complexity of the TDD and non-TDD projects are comparable..."
Perhaps more data needs to be collected.