Some Group Inspection Based Multi-Attribute Control Charts to Identify Process Deterioration

In a production process, when quality of the product depends on more than one characteristic, ‘Multivariate Quality Control’ (MQC) techniques are used. Many MQC techniques have been developed to control multivariate variable processes, but not much work has been reported on multivariate attribute processes. In this article, we propose some group inspection based multi-attribute control charts to identify process deterioration. The charts proposed are the ‘Multi-Attribute np’ (MA – np) chart, the ‘Multi-Attribute Synthetic’ (MA – Syn) chart and the ‘Multi-Attribute Group Runs’ (MA – GR) chart. The charts are developed by using MP-test based on the exact distribution. It is numerically illustrated that, MA – GR chart performs better than the other two charts. Also in steady state MA – GR chart performs better than MA – np and MA – Syn control charts. A procedure of identifying the attributes causing signal is also proposed.