The job of purchasing is obviously to source for reliable suppliers who deliver products conforming to specification on time within a certain price range. The more data is available about potential suppliers the better the decision will be. However, how shall the data be analysed?
FridgeMaker used to get supplies of a very crucial part, the Spacer, from Supplier X. Unfortunately, over the last months Supplier X has been struggling with waves of reorganisation resulting in unreliable deliveries and hence line stoppages for FridgeMaker.

Table 1: Supplier Qualification Data for Spacer (USL=10.8, LSL=10.2)

FridgeMaker is looking for new suppliers for all parts coming from Supplier X. Purchasing has already started the supplier qualification process for the Spacer (10.5 +/-0.3) and has received parts from suppliers A, B and C. The data are shown here. Following this data purchasing can make their decision on price. All of the suppliers meet the requirements set out in the tender document.   …