SQC Online offers easy-to-use calculators for various popular quality control procedures, based on ISO and other widely used standards. Launched in 2000, SQC Online has served millions of sampling plans to tens of thousands of users.
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.
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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.
| Calculator | What is it for? |
|---|---|
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Sampling plans for attribute (pass/fail) data |
| MIL-STD-414 ANSI/ASQC Z1.9, ISO 3951-1, BS 6002 |
Sampling plans for measurement data |
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 |
| Accept-on-Zero (c=0) sampling plans for continuous production | |
| 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" |
| 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.
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| 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 calculating Cp 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" |
| 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") |