3 - Jacobs University

The work of Wittmann and Bergholz (2006) provides an important method for assessment of
the effectiveness of quality auditing. An evaluation of the consistency between quality performance
of Volkswagen suppliers and their respective quality evaluation scores is therefore a good starting
point to assess the effectiveness of the implementation of quality auditing at Volkswagen Group in
particular and in the automotive industry in general. Consequently, a substantial part of this paper
is devoted to a set of studies, which investigate this relationship.
Performance information of Volkswagen Group suppliers was acquired from production plant
records and is compared to the perceived quality capability of the respective supplier production
processes provided by their quality auditing scores measured in percent. At this point the initial
hypothesis of this part of the analysis can be summarized in that suppliers which obtained higher
scores during the audit evaluation are expected to have fewer problems throughout the series delivery
and therefore better quality performance, and vice versa. Any discrepancies between the
evaluation scores of suppliers and their actual quality performance imply potential deficiencies of
the quality auditing routine and therefore identify particular areas which need closer examination.
On the other hand, best practice audit processes can be derived from cases which show good parity
between the two investigated quantities.
Two recent studies (Stroescu-Dabu, 2008; Hadzhiev, 2009) evaluate the effectiveness of
Volkswagen Group’s quality audit and employ the same analytical approach. These works already
outline important findings, which serve as a basis for the analysis presented here. The first
important point is the fact that the automotive supply network is characterized by a high level of
diversity. This is not surprising, provided its enormous scale and the great variety of individual
components, which are assembled in a car. Stroescu-Dabu (2008) uses a general supplier categorization
based on the type of industry in which each company operates. Suppliers are divided into
metal, chemical, and electrical suppliers. The analysis of Stroescu-Dabu (2008) shows that the
distribution of evaluation scores of electrical suppliers is statistically different than the evaluation
distributions of metal and chemical suppliers. The latter, on the other hand, have similar evaluation
score distributions. Furthermore, while in the electric industry auditing scores show relatively
good correspondence to the quality performance of the respective suppliers, for suppliers which
operate in the metal and chemical industries results do not provide any evidence that suppliers with
better audit scores perform better in terms of quality of the delivered components. This is a highly
undesired state of affairs and needs to be clarified.
In an attempt to narrow down the causes of these results Hadzhiev (2009) extends the findings
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