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SQC Online offers easy-to-use calculators for various popular quality control procedures, based on ISO and other widely used standards.

Acceptance Sampling: Accept or Reject Batches

Acceptance sampling is used by industries worldwide for assuring the quality of incoming and outgoing goods. Acceptance sampling plans determine the sample size and criteria for accepting or rejecting a batch based on the quality of a sample, using statistical principles. Many organizations require the use of ISO standards (or their ANSI/ASQC/BS/Military Standards or other counterparts) for purposes of certification. Below are online versions of Military Standard Tables (equivalent to the civilian ISO/ANSI/ASQC/BS standards), which greatly simplify the process of determining sampling plans. You can find out how many items to sample and inspect, and how to decide whether the entire batch should be accepted or rejected.

Tell me more about acceptance sampling.

Calculator What is it for?
MIL-STD-105E (ANSI/ASQ Z1.4)
ISO 2859-1 (BS 6001-1)
Sampling plans for attribute (pass/fail) data
MIL-STD-414
ANSI/ASQC Z1.9, ISO 3951, BS 6002
Sampling plans for measurement data
MIL-STD-1235C
Procedure CSP-1
Sampling plans for continuous production
Dodge-Romig Single Sampling AOQL AOQL-based rectifying plan for attribute (pass/fail) data
Dodge-Romig Single Sampling LTPD LTPD-based rectifying plan for attribute (pass/fail) data
MIL-STD-1916 for Attributes Accept-on-Zero (c=0) sampling plans for attribute (pass/fail) data
MIL-STD-1916 for Variables Accept-on-Zero (c=0) sampling plans for measurement data
MIL-STD-1916 for Continuous Sampling Accept-on-Zero (c=0) sampling plans for continuous production
Squeglia Zero-Based Plans AQL-based Accept-on-Zero (c=0) sampling plans for attribute (pass/fail) data
 
Procedure What is it for? Example
MIL-STD-105E Switching Rules (ANSI/ASQC Z1.4)
ISO 2859-1 Switching Rules (BS 6001-1)
Switching rules between levels of inspection "Switch from normal to tightened inspection following 5 consecutive accepted batches"
MIL-STD-1235C Switching Rules
Procedure CSP-1
Switching rules between phases of sampling "Switch from 100% inspection to partial sampling after 5 consecutive  conforming items" 
MIL-STD-1916 Switching Rules Switching rules for batch (attributes and variables) sampling plans Switch from normal to reduced inspection following 10 consecutive non-rejected batches



Control Charts: Is Your Process Out of Control?

A control chart is a popular statistical tool for monitoring the quality of goods and services, and for detecting when the process goes "out of control" as early as possible. Samples from the process are taken every time interval, and their quality measured. Control charts are used to track the sample quality over time and detect any unusual behavior. Below are calculators that help you to easily obtain the control chart limits for different types of measurements.

Tell me more about control charts.

Calculator What is it for? Example
Control Charts for Variables Compute limits for x, S and R control charts  
Control Charts for Attributes Compute limits for c, p, u and np  
Western Electric Company (WECO) Rules The detections of small shifts "Signal an alarm if 8 consecutive points fall on one side of the center line"



Process Capability

Does Your Process Meet Specifications?

Calculator What is it for?
Process Capability Index Find out if your process meets the specifications by calculatingCp and Cpk



Reliability of Systems and Components

Calculator What is it for? Example
Consecutive-Type System Reliability Compute the failure rate of consecutive-type systems "The system fails if 3 consecutive components fail"
MIL-HDBK-217 Calculate MTBF and failure rates for electrical and electronic components, devices, and equipment  
MTBF Calculator Calculate MTBF for a system, given the part (component) failure rate  



Learn about Run-Related Distributions

Many procedures in industry are based on the concept of a "run". A run is a sequence of identical events, such as a sequence of winnings in a slot machine. Many such procedures are based on rules of thumb, rather than on theory. Below is a calculator based on innovative theory developed in this field. The application shows what you should expect if applying a run-based procedure.

Procedure What is it for
Waiting for the First Run How long until you see the next run? Find the waiting time distribution for a specified run, given a sequence of independent success/failure events with the same probability of success ("IID bernouli trials")