Following on from zero defects, Philip Crosby put forward what became know as his Four Absolutes:
1) Quality is conformance to requirements, not elegance.
In its simplest form this means meeting the specification. If a metal bar is specified at 1.250m +/-25mm it needs to be no shorter than 1.225m nor longer than 1.275m – 1.224m is not acceptable (nor, if it could be measured, would 1.2249999999m). There is no grading of quality for, within this regime, something is right (has the required quality) or it isn’t.
2) It’s always cheaper to get it right first time
Talking about the economics of quality is a distraction. Inspection, repairs, scrap all cost more money than that needed to prevent repairs and scrap. This is the principle of the PAFF methodology for quality costing. I’m sure some people will be able to find exceptions (e.g. where it’s cheaper to buy or make cheap components and segregate out the rejects rather than buying or making good ones in the first place) but Crosby’s approach is still sound and rarely wrong when looking at the bigger picture.
3) The only performance standard is zero defects
Possibly a restatement of the first point but it needs to be applied throughout an organisation and for all processes. Paperwork should be right first time, drawings and designs shouldn’t require corrections when presented for review and approval, etc. The principle applies to management as much as to production.
4) The only performance measure is the cost of quality<
By cost of quality read cost of nonconformance – every cost that could have been avoided had everything been done right first time, returning to the second point.
In Quality is Free. Crosby actually had five absolutes – one that is often omitted:
5) There is no such thing as a quality problem
The problems that affect quality are fundamental to the organisation’s way of working. If I may use a medical analogy: symptoms are what a patient experiences as a result of a specific condition, signs are the external manifestation (e.g. why a doctor looks for or is otherwise able to detect or measure). Treating the signs is rarely satisfactory for the patient – symptomatic relief is a start but a cure is the ideal. Poor quality (failure to conform to the requirements in Crosby’s terms) is only a sign of a problem; the organisation has to identify the symptoms, find the source of the problem and treat it.