qa vs qc

huangyhg

qa vs qc
in the context of construction specifications, i've seen different definitions for the terms quality control and quality assurance.  aia masterspec defines quality assurance as "activities...performed before and during execution of work"  and quality control as "tests, inspections...during and after completion of the work."   
but i've also seen qc refering to control activities performed by a contractor, and qa as inspection of the contractor's work performed by others (who are separate from the contractor).
what are the conventional industry standards for the meanings of these words?
-jcali
   
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i think aia has it backwards.  quality can only be controlled during the process of work.  after the work is completed, it's too late to control the quality.  by then you can only inspect the work to assure that quality goals were met.  just my opinion though.
i look at the quality process in 3 steps...quality control, quality assurance, and quality verification.
quality control can only be done by one actually doing the work or in direct control of the work.  in the construction process, that would be the general contractor.  it is a process of activities done during the work to achieve quality.
quality assurance consists of a process set in place to help define the quality control process and who is responsible for what.  quality assurance can be a written document describing the steps to achieve quality through quality control.  specifications are part of a quality assurance program.
quality verification is the testing and inspection process that checks to see that a measurable or quantifiable process was completed in accordance with the established criteria.
quality assurance (qa) - an integrated system of management activities involving planning, implementation, assessment, reporting, and quality improvement to ensure that a process, item, or service is of the type and quality needed and expected by the customer. qa includes a system of quality controls backed by quality verification activities that demonstrate the completeness and appropriateness of achieved quality.
quality assurance record - a completed record that furnishes evidence of the quality of items and/or activities affecting quality.
quality control (qc) - those activities and criteria that measure the attributes and performance of a process, item, or service against defined standards to verify that they meet stated requirements, including operational techniques and activities that are used to fulfill requirements for quality.
scet - techmaximus
the contractor's inspector's are in a fuzzy area.  they often call themselves qa, because per the above definitions they're not part of process control, they're inspection after the fact.  but from the owner's point of view, they're all part of one big qc process before the product is handed over to the owner's inspectors, who are most definitely qa.
another definition i see a lot that probably doesn't line up with the quality industry is that qc, regardless of which party has responsibility, inspects everything, whereas qa is an audit function that makes sure that qc really is working.
hg
qc is a cost before the fact.
qa is a cost after the fact.
quality improvement is the sum of qc+qa
do the math to affect the product!