About SQC Online

SQC Online was created in 2000 as part of Professor Galit Shmueli's Ph.D. thesis on the theory of runs and scans. SQC Online's mission statement is to create a bridge between industry and academics, and provide free, accurate and accessible knowledge to the quality control community.

From its modest beginning 12 years ago, SQC Online has expanded in capabilities and grown to a website serving thousands of practitioners across multiple industries and continents, be it humble mom-and-pop operations or Fortune 500 companies.

SQC Online was originally hosted by the Israel Institute of Technology in Haifa.

With more than a 4,000,000 sampling plans served, we strive to serve the community in the years to come!

If you have any questions, don't hesitate to contact us.

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Quality is not an act, it is a habit.

— Aristotle

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The Perfect Companion to SQC Online

Practical Acceptance Sampling (2nd Edition) is a hands-on introduction to the inspection of products and services for quality assurance using statistically-based sampling plans.

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Methods are illustrated using SQC Online, Microsoft Excel, and online calculators.

From the Glossary

Alarm Zones

The zones in an ordinary 3-sigma control chart are beyond the upper control limit (3,∞), and below the lower control limit (-∞, -3).

To specify the alarm zone as the area between the warning limits and control limits, enter a=2, b=3.
In a control chart with 0.001 probability control limits (3.09 "sigma") and 0.025 warning limits (2.24 "sigma"), the rule "two consecutive points between the control and warning limits" is given by: k=2, a=2.24, b=3.09.
The zones are usually symmetric around the center line. For example: [-3,-2] and [2,3].

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The Perfect Companion to SQC Online

From the Glossary