Engineering makes a product work once; quality assurance makes it work every time
Long before factories, medieval guilds policed the standard of their members' goods, and an English king sent an overseer to inspect his ships. Quality assurance grew from those roots into a discipline built on prevention: catching the cause of a defect early, so faulty parts never get made at all.
Quality assurance and quality control are often treated as synonyms, but they aim at different moments. Control inspects what comes off the line and removes the bad items. Assurance works on the process upstream, measuring it against a standard and feeding the results back so errors are prevented. Engineers call this a shift left, because on a diagram read from left to right the effort moves earlier. Two slogans capture the idea: fit for purpose, and right first time.
The history runs through kings and clerks. William de Wrotham was tasked by King John of England with reporting on how ships were built and repaired, and centuries later Samuel Pepys, at the British Admiralty, used several overseers to standardise sea rations and naval training. Before the Industrial Revolution a craftsman could judge his own work; afterwards, large groups of specialised workers answered to a foreman charged with checking what they produced.
Mass production and piece work around the First World War made things worse, since workers paid per item had a reason to pass shoddy pieces along. Frederick Winslow Taylor broke jobs into simple steps and confined inspection to a few people, while Henry Ford pushed standard designs and placed machine inspectors in every department. At Bell Laboratories in the early 1920s, Walter A. Shewhart pioneered statistical process control, producing the control chart in 1924. His methods reached munitions work at the Picatinny Arsenal in 1934.
After the Second World War, General Douglas MacArthur brought W. Edwards Deming and Joseph Juran into the rebuilding of Japan, where their collaborative approach shaped industrial recovery. American manufacturers, by contrast, kept relying for decades on inspection and sampling to weed out defects. Modern practice adds stress testing, running a finished product under rising vibration, heat and humidity until it breaks, which can reveal fixes as modest as switching to mould-resistant paint.
Source: Quality assurance
