Gary
As db has stated SPC is not mandated by the ISO9001 standard, which is one of the worst crimes commited by the writers of this document.
My humble opinion for what its worth is that in order to understand the performance of your processes you MUST analyse them using proven statistical techniques. ISO9001 harps on about the importance of process management, yet fails to highlight the crucial part of process management, i.e. the understanding of variance, and need for statistical analysis of process performance.