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The Coordinating European Council, CEC, develops performance tests for the motor, oil, petroleum, additive and allied industries. In recent years, CEC has moved away from using round robin programmes (RRP's) for monitoring the precision and severity of test methods in favour of regular referencing within a test monitoring system (TMS). In a TMS, a reference sample of known performance, determined by cross-laboratory testing, is tested at regular intervals at each laboratory. The results are plotted on control charts and determine whether the installation is and continues to be fit to evaluate products. Results from all laboratories are collated and combined to monitor the general health of the test. The TMS approach offers considerable benefits in terms of detecting test problems and improving test quality. However, the effort required in collating data for statistical analysis is much greater, and there are technical difficulties in determining precision from TMS data.

Careful experimental design ensured that the EPEFE programme would deliver accurate, unambiguous conclusions despite the many pervading constraints on test fuels and test order. Fine-tuned statistical and graphical procedures were used methodically to identify possible outliers in the emissions data collected and to correct for underlying systematic trends. Summarising and interpreting the validated data required the rigorous use of advanced statistical modelling techniques which accounted correctly for both short- and long-term variability in emissions, and any unavoidable non-orthogonality or imbalance in the design. Multivariate methods were used for further data exploration.