Difference betwee SQC and SPC

Reshma,
The main difference is the scope of the statistics that is covered under SQC and SPC.
1. Purpose: SQC is used to monitor a quality or a process parameter, whereas SPC forms the basis on which all the statistical formulas and terms are defined and calculated.
2. Usage / application: SQC tools include all the graphical tools like control charts, which help to know whether the process is under control. SPC includes the whole spectrum of statistical terms and formulas, whic hare useful for process control as well as in inferential statistics.
3. Complexity: SPC is a more complex subject as compared to SQC, which have limited tools and techniques.
4. Coverage: The tools used in SQC form a part of SPC.
There may be few more points. Hope this helps.
Ajit

?
Whoever it was that said we need some foundation in Quality is right.
Lots of bad info floating around here today.

Stan is correct.  One of the classic books on SQC is Grant & Leavenworth, which consists of two major sections:  SPC and Acceptance Sampling.

Stan
Yes I agree that “SPC is a topic within SQC” – when we consider SQC as a functional area.
SQC got evolved only during 2nd world war, when the need for mass production and quality drive became the need of the hour. It was only during this phase, the ‘control charts’ was introduced by ‘Walter A. Stewhart’. In fact the credit for introducing the SQc goes to him. From this context, we can always say that tools used in SQC formed only a part of SPC. SQC was identified as a functional area, to control quality using control charts.
In today’s scenerio, it is clear that tools used in SPC, form a part of  ‘continous improvement’ tool kit. The function of ‘ SQC’ has become redundant, because in today’s scenerio, it is the responsibility of production dept. itself to control quality. The SQC function have been changed to ‘Quality Assurance’, which is  responsible for introducing and maintaining the ‘Quality Systems’. So from today’s scenerio, we can say that SPC forms a part of ‘Quality systems’. Since SQC itself is a merged entity, there is no question of  ‘SPC being a part of SQC’.
Your viewpoint is welcome.
Ajit