3 - Jacobs University

more than 60 production facilities on five continents and its global operations are supported by
more than 9000 direct business partners (1st-tier suppliers) 3 . Because of the large number of
suppliers, second-party auditing has received a central role in Volkswagen’s quality philosophy.
Furthermore, the scale of its global operations and the size of its supplier base provide a broad set
of empirical data, and therefore the opportunity for an in-depth analysis of the topic at hand. For
these reasons, Volkswagen Group is an ideal research object.
The essence of quality auditing at Volkswagen Group lies within regular evaluations of the
quality capability of suppliers’ production processes. As will be explained in detail later in this
paper a particular supplier quality audit lasts just several days and provides simply an assessment
of the momentary quality capability state of the evaluated production processes. On the other
hand, the long-term development of the quality capability of a particular production process can
be obtained only by a succession of quality audits at different points of time. Interestingly this
approach draws a lot of similarities with an important technique in the signal processing called
sampling. Sampling is used to convert analog to digital signals and is fundamental for areas such as
digital communications (Karrenberg, 2002; D’Antona & Ferrero, 2006). The idea behind sampling
is rather simple: ”the input signals are converted into a sequence of sampled values by means of a
sampling operation performed at given time instants, with a constant sampling period”, (D’Antona
& Ferrero, 2006, p. 33) . In practical terms this means that an analog (continuous in time) signal
(Figure 2a), such as speech for example, passes through an analog to digital (A/D) converter, which
converts it into a digitalized (discrete in time) copy of the original signal (Figure 2b). Proper
sampling reduces the amount of information contained within the original signal, but preserves the
main characteristics of the signal or system under study.
Most of the time analog signals contain a significant amount of redundant information, which
could be omitted and the core message be still transmitted. This less relevant information introduces
a computing overhead during the data processing cycle. Through sampling the amount of
information in the original signal is reduced and therefore its processing is simplified. A major
consideration in sampling, however, is to use enough samples in order to be able to completely
retrieve the essential information in the original signal from the sampled sequence (Karrenberg,
2002; D’Antona & Ferrero, 2006). Depending on the rate of variation of the individual continuoustime
signals, the frequency of the sampling measurements should be adjusted accordingly. If the
3 Source: personal communication with Volkswagen AG employees.
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