[CrimpJiggler]

In this diagram:

what exactly are they trying to convey as in, what is the relationship between TQM, QA, QS and QC? Does each outer circle encapsulate all the inner circles? For example, it QA a part of TQM, while QS is a part of QA etc.? I thought that QA and QC were 2 different things, I didn't think QC was just a subcategory of QA.

[Arkcon]

Yes, usually a Venn Diagram of this sort means exactly that: http://en.wikipedia.org/wiki/Venn_diagram  I recognize that the diagram seems a little prosaic, but it is accurate -- each outer level does supersede the inner one in authority, and each inner one does adds specificity the outer can't as it tries to be more inclusive.

[CrimpJiggler]

Ah I see. Thanks. So does the QA unit develop the quality system and the QC unit has to conform to it?

[Arkcon]

Yes.  Quality Control is concerned with, for example, specifications -- for example, a final product must have a certain pH +/- a certain range, as determined by an autotitrator, according to procedures listed in an SOP.  Quality Assurance would specify, for a group of products, including the product above, that the reported result be consistent across all products, and that QC SOPs and individual product documents are consistent.  The Total Quality Management would oversee a consistent policy and SOP's for Quality Assurance, as part of the companies overreaching stated goals.

It gets complicated rapidly -- I have worked at companies that produce fine chemicals where QC and QA were essentially the same people.  If I describe that situation to pharmaceutical manufacturers, they tend to almost fall out of their chair, they're horrified by the concept -- it seems like too much conflict of interest.  Which it would be, for something people consume when they're sick, but not for a bulk chemical reagent.

[JGK]

If you run an analysis for the company which employs you you produce results, the checks in place to ensure the anlysis is working and you are providing the correct result are described as Quality Control.

The organizational structure, procedures, processes and resources needed to implement the QC isthe Quality System (or more often as the quality management system, QMS)
 
Having all the aspects of the QMS procedure checked (audited) by an independent group to ensure you are following all the documented procedures required to perform the analysis and collect the data and generate the result is Quality Assurance.

Control and of all of the systems and infrastructure necessary for the company to provide you with the ability to perform your function is the scope of Total Quality Management