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Statistical Process Control (SPC) & Design of Experiments (DOE)

Numbers, numbers and numbers..........they tell you more than anyone can tell




Statistical process control (SPC) is the application of statistical methods to the monitoring and control of processes to ensure that they operate at their full potential to produce conforming products. With the application of SPC, processes behave predictably to produce as much conforming products as possible with the least possible waste. While SPC has been traditionally applied to controlling manufacturing lines, it applies equally well to any process with a measurable output. Key SPC tools are control charts, a focus on continuous improvement and designed experiments (DOE).


Much of the power of SPC lies in the ability to examine a process and the sources of variation in that process using tools that give weight to objective analysis over subjective opinions and that allow the strength of each source to be determined numerically. Variations in the process potentially affecting the quality of the end product or service can be detected and corrected, thereby reducing waste as well as the likelihood that problems will be passed on to the customers. With its emphasis on early detection and prevention of problems, SPC has a distinct advantage over other quality methods, such as inspection, that apply resources to detecting and correcting problems after they have occurred.


In addition to reducing waste, SPC can reduce the time required to produce a product or service from end to end. This is partially due to a diminished likelihood that the final product will have to be reworked, but it may also result from using SPC data to identify bottlenecks, wait times, and other sources of delays within the process. Process cycle time reductions coupled with improvements in yield have made SPC a valuable tool from both a cost reduction and a customer satisfaction standpoint.

Statistical Process Control (SPC) may be broadly broken down into three sets of activities:

  1. Understanding the processes,

  2. Understanding the causes of variation,

  3. Elimination of the sources of special cause variation


To understand a process, the process is typically mapped out and monitored using control charts. Control charts are used to identify variation that may be due to special causes, and to free the user from concern over variation due to common causes. Control charts make the understanding of the process a continuous ongoing activity. With a stable process that does not trigger any of the detection rules for a control chart, a process capability analysis is also performed to evaluate the ability of the current process to produce conforming products (products that are within specifications).


When, through the control charts, variation that is due to special causes is identified, or the process capability is found lacking, additional effort is exerted to determine causes of that variance and eliminate it. The tools used for this purpose include Ishikawa diagrams, Design of Experiments (DOE) and Pareto charts. Designed experiments (DOE) are critical to this phase of SPC, as they are the only means of objectively quantifying the relative importance of the many potential causes of variation.


Once the causes of variation are quantified, effort is spent in eliminating those causes that are both statistically and practically significant. This means a cause that has a only small but statistically significant effect may not be considered cost-effective to fix; and conversely, a cause that is not statistically significant cannot be considered practically significant. Additional measures may be required, especially if there is a problem with process capability.



Design of Experiments, or experimental design, (DoE) is a systematic method to determine the relationship between factors affecting a process and the output of that process. In other words, it is used to find cause-and-effect relationships. This information is needed to manage process inputs in order to optimize the output. This branch of applied statistics deals with planning, conducting, analyzing and interpreting controlled tests to evaluate the factors that control the value of a parameter or group of parameters. Strategically planned and executed experiments can provide a great deal of information about the effect on a response variable due to one or more factors. Design of experiments (DOE) is a discipline that has very broad application across all the natural and social sciences.


Our experienced manufacturing engineers are ready to guide you in implementing SPC and DOE concepts in your company. Depending on your choice, we can either remotely assist you or come and establish a working Statistical Process Control (SPC) system at your site. Here is a summary of services we provide our clients in the field of Statistical Process Control (SPC) and Design of Experiments (DoE):

  • SPC and DoE Consulting

  • SPC and DoE Training & Lecturing (web based, on-site or off-site)

  • SPC and DoE Project Support

  • Real-Time SPC Software Solutions, automating quality data collection and analysis, customization of software and applications if needed

  • Data Integration Tools Sale & Deployment

  • Sale & Deployment of Data Collection Hardware Components

  • Discovery and Site Assessment

  • Initial Launch

  • Expanded Deployment

  • Data Integration

  • Gap Analysis

  • Validation

  • Turn-Key SPC and DOE Solutions




AGS-Engineering will help you maximize your SPC system based on your unique situation. From initial assessments that can help you plan out your deployment, to validation services for businesses that need to meet regulatory or other demands, we will assist you and have you covered.


Expert site assessments from us or our trained service providers will provide you a comprehensive roadmap for planning, implementing, and managing a real-time quality intelligence and statistical process control (SPC) system. Our plan can help you to determine the time frame and implementation schedule that makes the most sense for your business. This roadmap will be a valuable tool for a winning quality control solution.


At the beginning, our SPC experts will work with you to discover your greatest needs or areas of opportunity. We will help you evaluate and verify your environment, identify your priorities, and we will jointly with you set target dates.


Based on what we learn during this discovery phase, we will help you plan a deployment strategy that will enable you to begin using our proposed solution as quickly as possible, while considering any need to build and expand the reach of your deployment as you move forward.



For organizations that want to deploy a pilot to test one of our SPC solutions in one site, we begin with an accelerated launch program. With this approach we activate the solution and create integrated processes and workflows that are proven to improve quality metrics. Using this accelerated launch we offer the quickest means for achieving important milestones, such as: Beginning to enter quality data on the shop floor, importing appropriate specification limits into the SPC system, providing real-time visibility for management into processes or product quality issues, creating management roll-ups, reports, and summaries of quality data, monitoring and displaying alarms that indicate out-of-control or out-of-specification conditions, activation of email alerts, and maybe more if needed or desired.



Our expanded deployment service is for businesses that need or choose to move beyond the initial phase. This service phase focuses on incorporating automated data collection methods, from manual operator input to electronic data collection. This phase enables you to reach important milestones for more complex environments, by automating data collection from electronic devices such as scales and hand-held gauges, expanding the use of quality intelligence and SPC throughout the plant and even across different sites, enhancing the depth and spectrum of management reporting, creating reports for communicating with management, customers, and suppliers


Enterprise-wide deployments for larger corporations offer the ability to complete implementation across all facilities and even into supply chains. With expanded deployment, our client’s entire database structure is organized and populated, correct statistical tools are selected, projects are developed, workstations and gauges are set up, and all appropriate training is conducted. Process data is collected, such as machine speeds, feeds, environmental parameters, a complete picture of product and process quality is developed for analysts, automatic integration of data from other systems is achieved, such as from enterprise resource planning (ERP), metrics and activities from across the production processes are captured and shared, updated reporting including additional data sources is accomplished.



Our solutions are designed to work with your existing business system software. Many of our customers need our SPC systems to communicate with existing systems such as laboratory information management system (LIMS), and ERP systems. Fortunately, our systems open architecture makes this type of communication possible.


To accelerate data integration, we offer integration tools, software components, data collection hardware components, and professional technical support services.



To make sure you are getting the most out of your solution, our on-site gap analysis can help you determine how to enhance and improve your deployment. Our seasoned SPC applications engineers evaluate your existing implementation and deliver expert suggestions for how to optimize your use of our software and other tools. Questions such as the following can be answered: How can I simplify the system for shop floor operators? How can data collection be more efficient? How can data from critical systems be consolidated? How can reports be improved to provide powerful, actionable information for managers? Whether you want to optimize results or establish a roadmap for improving the performance of your quality system, AGS-Engineering can offer expert assessment services to help you maximize your deployment.



Our Validation Package provides essential elements for system qualification, including Installation Verification and Operational Qualification documentation and a validation protocol. A basic functional requirements specification document is provided with the Installation Verification / Operational Qualification protocol. The Validation Package also includes a preformatted database.

Test cases are a primary part of the Validation package. The Installation Verification documentation consists of test cases to verify that components of our SPC Manufacturing Intelligence have been installed properly according to recommendations and documentation. The Operational Qualifications documentation consists of test cases to verify that key components of the SPC software are operating properly according to specifications. The Operational Qualifications can also be used to validate software sampling requirements through use of the Dynamic Scheduler.

Installation Verification and Operational Qualifications verification test cases include System Documentation, Standard Operating Procedures, Database Manager Installation, SPC Manufacturing Intelligence Installation, Dynamic Scheduler Installation, Operational Qualification.


Installation Verification and Operational Qualifications setup and operational qualification test cases include Reason for Change and Security Policy, Organization and Roles, Employees, Part Groups and Parts, Process Groups and Processes, Defect/Defective Groups and Codes, Test/Feature Groups and Tests, Descriptor Category and Descriptors, Lots, Assignable Cause Group and Corrective Action Groups, Corrective Action Codes, Assignable Cause Codes, Alarms, Specification Limits, Sampling Requirements, Project and Data Configuration Setup, Subgroup Data Entry, Control Limits, Alarms, Warning Messages, Equation Calculation, Regulatory Compliance (System Access, Password Aging, Electronic Records)

If you need to perform a formal software validation but lack the resources to meet an aggressive implementation schedule, we can assist with the execution of the Installation Verification and Operational Qualifications protocol.


In our Expert Validation package, the Performance Qualification (PQ) verifies the operation of the SPC software. It confirms that the system performs as intended and satisfies defined and approved user requirements and user-provided test case prerequisite data. The Performance Qualification is carried out by every user of the software in client’s organization. Additional services are provided to help develop user requirements and to prepare and execute customized Performance Qualification protocols. The VSR (Validation Summary Report) summarizes the results of the execution of test cases and documents the acceptance or rejection of the system for production use. Just as the Performance Qualification, the Validation Summary Report (VSR) is the responsibility of the users in your enterprise.

The Expert Validation Package is a self-contained protocol providing:

  • Introduction

  • Scope

  • Roles and Responsibilities

  • Review & Approval Signoff

  • Revision History

  • Description of the System

  • Glossary of Terms

  • Test Strategy (including Scope, Approach, Acceptance Criteria)

  • Test Organization

  • Handling of Deviations

  • Execution Procedure & Test Review

  • Test Cases

  • Deviation Report Log and Form

  • Signature Log

  • Data Sets

  • Expected Results


All test cases in the Expert Validation package include:

  • Instructions

  • Test Requirements

  • Acceptance Criteria

  • Steps

  • Expected Results

  • Pass/Fail Categorization

  • Executor Signoff and Dating

  • Reviewer Signoff and Dating

  • Comments


For more information regarding the SPC process and available tools, mentoring, training or assistance in implementing of SPC, contact one of our Subject Matter Experts (SME). We are ready to provide any assistance or information to add value to your enterprise.


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