The Shewhart p Chart for Comparisons (PDF, 39 KB) An important question regarding test result validity is, Given a positive test result, what is the probability that this test result is wrong? This question is answered by the positive predictive error rate, the number of false positive test results divided by the total number of positive test results.
SPC: From Chaos to Wiping the Floor (PDF, 151 KB) A history of statistical process control shows how it has gone from taming manufacturing processes to enabling all organizations to maintain their competitive edge.
Chicken Soup for Processes (PDF, 60 KB) Understanding process variation is a prerequisite to Using SPC.
Controversies and Contradictions in SPC (PDF, 147 KB) Areas of controversy in SPC include the relationship between hypothesis testing and control charting, the role of theory and the modeling of control chart performance, the relative merits of competing methods, the relevance of research on SPC and even the relevance of SPC itself.