SPC Calculations

SPC calculations business slide

Prior to conducting SPC calculations for the X bar and R chart make sure you gather your data. When gathering the data keep in mind these guidelines.

  • Select a sample size from 2 – 8 parts*.
  • Collect at least 25 groups of samples
  • Take the data over a period of a couple days
  • Select random lots and parts
  • Select random operators and machines.
  • Plot the data on a histogram and assure the data is normally distributed.

* Do not change the sample size after you start collecting your data and plotting the points.

Learn SPC in an hour. Train your employees. Improve your processes and products. Prevent defects and save your company money.

SPC Training Video

Limit SPC Calculations

1) For each group of samples calculate the mean and the range.

2) Calculate the overall mean which is know as  

3) Calculate the mean of all of the ranges. This is known as

4) Now you are ready to calculate the limits. See below for the equations

Learn SPC in an hour. Train your employees. Improve your processes and products. Prevent defects and save your company money.

SPC Training Video

Here is the table for the constants. The constants depend on your sample size.

Comment Box is loading comments...

More Info

  • Download Today. The number one mistake company’s make when implementing SPC is not training their employees in SPC. Maximize your SPC efforts! Get SPC help. Use this SPC Training Video to quickly train your staff. $69.00. Satisfaction guaranteed.

    SPC Help Video

    Download Today. The number one mistake company’s make when implementing SPC is not training their employees in SPC. Maximize your SPC efforts! Get SPC help. Use this SPC Training Video to quickly train your staff. $69.00. Satisfaction guaranteed.

  • Learn to audit your SPC inspection program. This article covers SPC technology keys such as documentation, training, reviewing, and process improvement.

    Auditing SPC inspection

    Learn to audit your SPC inspection program. This article covers SPC technology keys such as documentation, training, reviewing, and process improvement.

  • Here we discuss the SPC definition. We describe the charts and the meaning of "special cause variation". Read more...

    SPC definition

    Here we discuss the SPC definition. We describe the charts and the meaning of "special cause variation". Read more...

  • Learn about control chart SPC and the differences between process limits and specification. Article includes pictures of these limits with control charts.

    Control Chart SPC, Control Charts and limits

    Learn about control chart SPC and the differences between process limits and specification. Article includes pictures of these limits with control charts.

  • Control Charts, Variable data, Attribute data, Variation, Total Quality Management Tool

    Control Charts

    Control Charts, Variable data, Attribute data, Variation, Total Quality Management Tool

  • This article covers a roadmap for statistical process control. Discusses chart structure and implementation mistakes.

    statistical process control

    This article covers a roadmap for statistical process control. Discusses chart structure and implementation mistakes.


Quality Assurance Solutions
Robert Broughton
(805) 419-3344
USA
email
Enjoy this page? Please pay it forward. Here's how...

Would you prefer to share this page with others by linking to it?

  1. Click on the HTML link code below.
  2. Copy and paste it, adding a note of your own, into your blog, a Web page, forums, a blog comment, your Facebook account, or anywhere that someone would find this page valuable.

All Products

Software, Videos, Manuals, On-Line Certifications

PDCA Complete

An Organizational Task Management System. Projects, Meetings, Audits & more

8D Manager

Corrective Action Software

TrainingKeeper Software

Plan and Track Training

Snap Sampling Plans!

AQL Inspection Software

QAS Business Slide Deck

450+ Editable Slides with support links

TRIZ Kit

Learn and Train TRIZ

ISO 9001:2015 QA Manual

Editable Template

ISO 9001:2015 QMS Kit

Templates, Guides, QA Manual, Audit Checklists

ISO 14001:2015 EMS Kit

EMS Manual, Procedures, Forms, Examples, Audits, Videos

On-Line Accredited Certifications

Six Sigma, Risk Management, SCRUM

All Products

Software, Videos, Manuals, On-Line Certifications