VDA-Volume 4: Elementary Aids 1 We would like to thank all the companies and their staff who have contri- buted to this workgroup: AUDI AG, Ingolstadt BMW AG, Munich Robert Bosch GmbH, Stuttgart Continental AG, Hannover DGQ (Deutsche Gesellschaft fr Qualitt), Frankfurt Fichtel this means that A and B items (or A and B parts) together cause 94.4 % of the repair/rework time. Area C: The remaining seven parts (50% of the examined parts) are responsible for only 5.6% of the repair/rework time. VDA-Volume 4: Elementary Aids 10 VDA-Volume 4: Elementary Aids 11 ABC analysis for costs Using the ABC analysis, it is possible to recognize the parts for which measures for preventing nonconformities would most effectively lead to a reduction in the internal repair/rework costs. If the costs for a unit of time of rework are not the same for all parts, the question that arises is whether the A parts determined in the example also cause the highest rework costs. This question is answered by a further ABC analysis using the costs for the different types of rework. For each part, the necessary rework time is multiplied by the specific rework costs (for example, euros/minute). This results in the total costs for rewor- king these 14 parts. In this way, it is possible to determine the share, in percent, that each part contributes to the total rework costs. These values are then entered in the Pareto diagram in the manner already shown, and subsequently the ABC areas are determined again. 1.8 Scatter Plot The correlation or scatter plot enables a graphical representation of pairs of values, in order to investigate possible relationships between two variables. It is possible to recognize how a dependent variable y changes when an independent variable x changes. Example: - Change in the number of calculation errors for different people with different uninterrupted computational hours. 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 Number of calculation errors/d Average computational hours/day 8 9 10 ay y x y x y x positive correlation no correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . negative correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 12.8 Correlation or Scatter Plot with Positive Correlation VDA-Volume 4: Elementary Aids 12 VDA-Volume 4: Elementary Aids 13