{"id":46,"date":"2022-07-21T15:16:34","date_gmt":"2022-07-21T15:16:34","guid":{"rendered":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/?post_type=chapter&#038;p=46"},"modified":"2022-11-02T10:59:30","modified_gmt":"2022-11-02T10:59:30","slug":"chapter-10a","status":"publish","type":"chapter","link":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/chapter\/chapter-10a\/","title":{"raw":"Chapter 10: Is the Process Stable?","rendered":"Chapter 10: Is the Process Stable?"},"content":{"raw":"<h2>Chapter 10: Is the Process Stable?<\/h2>\r\n\r\n<hr \/>\r\n\r\n<h2>A Stable Process<\/h2>\r\nAll processes have variation and the products will vary. However, stable processes are only being influenced by common cause variation and this common cause variation is predictable. When a process is influenced by a special cause variation it is not predictable or stable.\r\n\r\nIn statistical process control, we aim to create a stable process and then monitor the stability so we can easily identify when the special cause variation occurs. Therefore, the first steps is to check for process stability.\r\n<h3>AIAG Method for SPC<\/h3>\r\nThis content is from the Automotive Industry Action Group which provides education and information to a wide range of people. Their process of using SPC and maintaining control is outline below, but originated from this source: <a href=\"https:\/\/www.aiag.org\/quality\/automotive-core-tools\/spc\" target=\"_blank\" rel=\"noopener\">(SPC) Statistical Process Control<\/a> (AIAG, 2022). Learn more by selecting the link.\r\n<blockquote>There are two phases in SPC control studies:\r\n<ul>\r\n \t<li>Identify and eliminate the special causes of variation in the process. This will stabilize the process and provide control.<\/li>\r\n \t<li>Next, predict future data based on the control data. Once stabilized, the process can be used to determine capability.<\/li>\r\n<\/ul>\r\n<\/blockquote>\r\n[h5p id=\"34\"]\r\n<h2>Determining Stability<\/h2>\r\n[caption id=\"attachment_353\" align=\"alignleft\" width=\"369\"]<img class=\" wp-image-353\" src=\"http:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/automotive-300x200.jpg\" alt=\"&quot;Automotive Industry&quot; by bisgovuk is licensed under CC BY-ND 2.0. \" width=\"369\" height=\"246\" \/> \"<a href=\"https:\/\/www.flickr.com\/photos\/39161050@N03\/5886951275\" target=\"_blank\" rel=\"noopener noreferrer\">Automotive Industry<\/a>\" by <a href=\"https:\/\/www.flickr.com\/photos\/39161050@N03\" target=\"_blank\" rel=\"noopener noreferrer\">bisgovuk<\/a> is licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by-nd\/2.0\/?ref=openverse\" target=\"_blank\" rel=\"noopener noreferrer\">CC BY-ND 2.0<\/a>.[\/caption]\r\n\r\nIf the process is not stable, the data would not be reliable enough to estimate anything, whether its future performance of capability of a lot of things (Haynes, 2022). In these situations, you will examine the data for non-normal conditions and\/or outliers and typically, run the assessment again (van de Merbel et al., 2014).\r\n\r\nThe tool used to determine stability is a histogram and often run charts. Histograms which are not normal are often an indicator of instability. Additionally, monitoring the histogram over time can prove stability - stable process histogram would be consistent in size and shape over time. Typically a study of more than 100 samples are logged over a long period of time and are utilized to create the histogram and\/or run charts. It can be beneficial to monitor the mean, sigma, and also the calculated control limits at the +\/-3 sigma values. A stable process has a constant mean and a constant variance\/sigma over time. I\r\n\r\nIf the process is not stable then SPC cannot yet be utilized. Problem-solving to determine and eliminated the special causes of variation must be conducted. Tools such as a fishbone diagram can help identify and brainstorm the possible sources of variation.\r\n\r\n[caption id=\"attachment_431\" align=\"aligncenter\" width=\"419\"]<img class=\" wp-image-431\" src=\"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/stable-300x225.jpg\" alt=\"stability capability and sigma level of process quality\" width=\"419\" height=\"314\" \/> Stability, capability, and sigma level of process quality[\/caption]\r\n\r\nLearn more about a common stability analysis method by selecting the following link: <a href=\"https:\/\/www.qimacros.com\/control-chart\/stability-analysis-control-chart-rules\/\" target=\"_blank\" rel=\"noopener\">Stability Analysis Control Chart<\/a>\r\n<h2>Value of a Histogram<\/h2>\r\nA histogram is a visual representation of data, which the viewer can generally understand easily and interpret the data. Histograms are used when evaluating data that is continuous and counted as separate distinct values (or discrete data). Histograms are valuable to convey information effectively and to show changes implemented within a process (Presentationeze, 2013). Histograms can also identify outliers in a process (Frost, 2019). Learn more about <a href=\"https:\/\/statisticsbyjim.com\/basics\/histograms\/\">using histograms to understand data<\/a> with this article.\r\n<h2>Test Yourself<\/h2>\r\nReview the each of the hot spots below on the histogram. Then, answer the review questions to test your knowledge.\r\n\r\n&nbsp;\r\n\r\n[h5p id=\"36\"]\r\n\r\n&nbsp;\r\n\r\n[h5p id=\"37\"]\r\n\r\n<hr \/>\r\n\r\n<h2>References<\/h2>\r\n<p class=\"hanging-indent\">Automotive Industry Action Group (2022). <em>(SPC) Statistical process control. <\/em>AIAG. Retrieved on August 8, 2022 from <a href=\"https:\/\/www.aiag.org\/quality\/automotive-core-tools\/spc\">https:\/\/www.aiag.org\/quality\/automotive-core-tools\/spc<\/a><\/p>\r\n<p class=\"hanging-indent\">Benchmark 6ix Sigma (2017). <em>Process stability, process capability. <\/em>Retrieved on August 8, 2022 from <a href=\"https:\/\/www.benchmarksixsigma.com\/forum\/topic\/34898-process-stability-process-capability\/\">https:\/\/www.benchmarksixsigma.com\/forum\/topic\/34898-process-stability-process-capability\/<\/a><\/p>\r\n<p class=\"hanging-indent\">Cordaro, C. (2013, September 16). <em>Process stability <\/em>[Video]. YouTube. <a href=\"https:\/\/www.youtube.com\/watch?v=tTRJ2vNvr3M\">https:\/\/www.youtube.com\/watch?v=tTRJ2vNvr3M<\/a><\/p>\r\n<p class=\"hanging-indent\">Frost, J. (2019). <em>Using histograms to understand your data. <\/em>Retrieved on August 8, 2022 from <a href=\"https:\/\/statisticsbyjim.com\/basics\/histograms\/\">https:\/\/statisticsbyjim.com\/basics\/histograms\/<\/a><\/p>\r\n<p class=\"hanging-indent\">IST\/SEMATECH<i>. <\/i>(2012)<i>. e-Handbook of Statistical Methods. <\/i>Retrieved on August 8, 2022 from <a href=\"http:\/\/IST\/SEMATECH e-Handbook of Statistical Methods, http:\/\/www.itl.nist.gov\/div898\/handbook\/, date. (Links to specific pages can also be referenced this way, if suitable.)\">http:\/\/www.itl.nist.gov\/div898\/handbook\/<\/a><\/p>\r\n<p class=\"hanging-indent\">ISIXSIGMA (2022). <em>Process stability. <a href=\"https:\/\/www.isixsigma.com\/dictionary\/process-stability\/\">https:\/\/www.isixsigma.com\/dictionary\/process-stability\/<\/a><\/em><\/p>\r\nSPC for Excel (2019, May 1). <em>What do these histograms tell you? The answers <\/em>[Video]. YouTube. <a href=\"https:\/\/www.youtube.com\/watch?v=XUeU4tvkXAo\">https:\/\/www.youtube.com\/watch?v=XUeU4tvkXAo<\/a>\r\n<p class=\"citation-text hanging-indent\">van de Merbel N, Savoie N, Yadav M, Ohtsu Y, White J, Riccio MF, Dong K, de Vries R, &amp; Diancin J. 2014 Feb 19.Stability: recommendation for best practices and harmonization from the Global Bioanalysis Consortium Harmonization Team. AAPS J. 2014 May;16(3):392-9. doi: 10.1208\/s12248-014-9573-z. Epub\u00a0 PMID: 24550081; PMCID: PMC4012051.<\/p>","rendered":"<h2>Chapter 10: Is the Process Stable?<\/h2>\n<hr \/>\n<h2>A Stable Process<\/h2>\n<p>All processes have variation and the products will vary. However, stable processes are only being influenced by common cause variation and this common cause variation is predictable. When a process is influenced by a special cause variation it is not predictable or stable.<\/p>\n<p>In statistical process control, we aim to create a stable process and then monitor the stability so we can easily identify when the special cause variation occurs. Therefore, the first steps is to check for process stability.<\/p>\n<h3>AIAG Method for SPC<\/h3>\n<p>This content is from the Automotive Industry Action Group which provides education and information to a wide range of people. Their process of using SPC and maintaining control is outline below, but originated from this source: <a href=\"https:\/\/www.aiag.org\/quality\/automotive-core-tools\/spc\" target=\"_blank\" rel=\"noopener\">(SPC) Statistical Process Control<\/a> (AIAG, 2022). Learn more by selecting the link.<\/p>\n<blockquote><p>There are two phases in SPC control studies:<\/p>\n<ul>\n<li>Identify and eliminate the special causes of variation in the process. This will stabilize the process and provide control.<\/li>\n<li>Next, predict future data based on the control data. Once stabilized, the process can be used to determine capability.<\/li>\n<\/ul>\n<\/blockquote>\n<div id=\"h5p-34\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-34\" class=\"h5p-iframe\" data-content-id=\"34\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Process Stability\"><\/iframe><\/div>\n<\/div>\n<h2>Determining Stability<\/h2>\n<figure id=\"attachment_353\" aria-describedby=\"caption-attachment-353\" style=\"width: 369px\" class=\"wp-caption alignleft\"><img class=\"wp-image-353\" src=\"http:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/automotive-300x200.jpg\" alt=\"&quot;Automotive Industry&quot; by bisgovuk is licensed under CC BY-ND 2.0.\" width=\"369\" height=\"246\" srcset=\"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/automotive-300x200.jpg 300w, https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/automotive-768x512.jpg 768w, https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/automotive-65x43.jpg 65w, https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/automotive-225x150.jpg 225w, https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/automotive-350x233.jpg 350w, https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/automotive.jpg 1024w\" \/><figcaption id=\"caption-attachment-353\" class=\"wp-caption-text\">&#8220;<a href=\"https:\/\/www.flickr.com\/photos\/39161050@N03\/5886951275\" target=\"_blank\" rel=\"noopener noreferrer\">Automotive Industry<\/a>&#8221; by <a href=\"https:\/\/www.flickr.com\/photos\/39161050@N03\" target=\"_blank\" rel=\"noopener noreferrer\">bisgovuk<\/a> is licensed under <a href=\"https:\/\/creativecommons.org\/licenses\/by-nd\/2.0\/?ref=openverse\" target=\"_blank\" rel=\"noopener noreferrer\">CC BY-ND 2.0<\/a>.<\/figcaption><\/figure>\n<p>If the process is not stable, the data would not be reliable enough to estimate anything, whether its future performance of capability of a lot of things (Haynes, 2022). In these situations, you will examine the data for non-normal conditions and\/or outliers and typically, run the assessment again (van de Merbel et al., 2014).<\/p>\n<p>The tool used to determine stability is a histogram and often run charts. Histograms which are not normal are often an indicator of instability. Additionally, monitoring the histogram over time can prove stability &#8211; stable process histogram would be consistent in size and shape over time. Typically a study of more than 100 samples are logged over a long period of time and are utilized to create the histogram and\/or run charts. It can be beneficial to monitor the mean, sigma, and also the calculated control limits at the +\/-3 sigma values. A stable process has a constant mean and a constant variance\/sigma over time. I<\/p>\n<p>If the process is not stable then SPC cannot yet be utilized. Problem-solving to determine and eliminated the special causes of variation must be conducted. Tools such as a fishbone diagram can help identify and brainstorm the possible sources of variation.<\/p>\n<figure id=\"attachment_431\" aria-describedby=\"caption-attachment-431\" style=\"width: 419px\" class=\"wp-caption aligncenter\"><img class=\"wp-image-431\" src=\"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/stable-300x225.jpg\" alt=\"stability capability and sigma level of process quality\" width=\"419\" height=\"314\" srcset=\"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/stable-300x225.jpg 300w, https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/stable-65x49.jpg 65w, https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/stable-225x169.jpg 225w, https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/stable-350x263.jpg 350w, https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-content\/uploads\/sites\/37\/2022\/07\/stable.jpg 361w\" \/><figcaption id=\"caption-attachment-431\" class=\"wp-caption-text\">Stability, capability, and sigma level of process quality<\/figcaption><\/figure>\n<p>Learn more about a common stability analysis method by selecting the following link: <a href=\"https:\/\/www.qimacros.com\/control-chart\/stability-analysis-control-chart-rules\/\" target=\"_blank\" rel=\"noopener\">Stability Analysis Control Chart<\/a><\/p>\n<h2>Value of a Histogram<\/h2>\n<p>A histogram is a visual representation of data, which the viewer can generally understand easily and interpret the data. Histograms are used when evaluating data that is continuous and counted as separate distinct values (or discrete data). Histograms are valuable to convey information effectively and to show changes implemented within a process (Presentationeze, 2013). Histograms can also identify outliers in a process (Frost, 2019). Learn more about <a href=\"https:\/\/statisticsbyjim.com\/basics\/histograms\/\">using histograms to understand data<\/a> with this article.<\/p>\n<h2>Test Yourself<\/h2>\n<p>Review the each of the hot spots below on the histogram. Then, answer the review questions to test your knowledge.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"h5p-36\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-36\" class=\"h5p-iframe\" data-content-id=\"36\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Bell Curve\"><\/iframe><\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<div id=\"h5p-37\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-37\" class=\"h5p-iframe\" data-content-id=\"37\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Review of histogram\"><\/iframe><\/div>\n<\/div>\n<hr \/>\n<h2>References<\/h2>\n<p class=\"hanging-indent\">Automotive Industry Action Group (2022). <em>(SPC) Statistical process control. <\/em>AIAG. Retrieved on August 8, 2022 from <a href=\"https:\/\/www.aiag.org\/quality\/automotive-core-tools\/spc\">https:\/\/www.aiag.org\/quality\/automotive-core-tools\/spc<\/a><\/p>\n<p class=\"hanging-indent\">Benchmark 6ix Sigma (2017). <em>Process stability, process capability. <\/em>Retrieved on August 8, 2022 from <a href=\"https:\/\/www.benchmarksixsigma.com\/forum\/topic\/34898-process-stability-process-capability\/\">https:\/\/www.benchmarksixsigma.com\/forum\/topic\/34898-process-stability-process-capability\/<\/a><\/p>\n<p class=\"hanging-indent\">Cordaro, C. (2013, September 16). <em>Process stability <\/em>[Video]. YouTube. <a href=\"https:\/\/www.youtube.com\/watch?v=tTRJ2vNvr3M\">https:\/\/www.youtube.com\/watch?v=tTRJ2vNvr3M<\/a><\/p>\n<p class=\"hanging-indent\">Frost, J. (2019). <em>Using histograms to understand your data. <\/em>Retrieved on August 8, 2022 from <a href=\"https:\/\/statisticsbyjim.com\/basics\/histograms\/\">https:\/\/statisticsbyjim.com\/basics\/histograms\/<\/a><\/p>\n<p class=\"hanging-indent\">IST\/SEMATECH<i>. <\/i>(2012)<i>. e-Handbook of Statistical Methods. <\/i>Retrieved on August 8, 2022 from <a href=\"http:\/\/IST\/SEMATECH e-Handbook of Statistical Methods, http:\/\/www.itl.nist.gov\/div898\/handbook\/, date. (Links to specific pages can also be referenced this way, if suitable.)\">http:\/\/www.itl.nist.gov\/div898\/handbook\/<\/a><\/p>\n<p class=\"hanging-indent\">ISIXSIGMA (2022). <em>Process stability. <a href=\"https:\/\/www.isixsigma.com\/dictionary\/process-stability\/\">https:\/\/www.isixsigma.com\/dictionary\/process-stability\/<\/a><\/em><\/p>\n<p>SPC for Excel (2019, May 1). <em>What do these histograms tell you? The answers <\/em>[Video]. YouTube. <a href=\"https:\/\/www.youtube.com\/watch?v=XUeU4tvkXAo\">https:\/\/www.youtube.com\/watch?v=XUeU4tvkXAo<\/a><\/p>\n<p class=\"citation-text hanging-indent\">van de Merbel N, Savoie N, Yadav M, Ohtsu Y, White J, Riccio MF, Dong K, de Vries R, &amp; Diancin J. 2014 Feb 19.Stability: recommendation for best practices and harmonization from the Global Bioanalysis Consortium Harmonization Team. AAPS J. 2014 May;16(3):392-9. doi: 10.1208\/s12248-014-9573-z. Epub\u00a0 PMID: 24550081; PMCID: PMC4012051.<\/p>\n","protected":false},"author":20,"menu_order":10,"template":"","meta":{"pb_show_title":"","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[49],"contributor":[],"license":[],"part":3,"_links":{"self":[{"href":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-json\/pressbooks\/v2\/chapters\/46"}],"collection":[{"href":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-json\/wp\/v2\/users\/20"}],"version-history":[{"count":21,"href":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-json\/pressbooks\/v2\/chapters\/46\/revisions"}],"predecessor-version":[{"id":437,"href":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-json\/pressbooks\/v2\/chapters\/46\/revisions\/437"}],"part":[{"href":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-json\/pressbooks\/v2\/parts\/3"}],"metadata":[{"href":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-json\/pressbooks\/v2\/chapters\/46\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-json\/wp\/v2\/media?parent=46"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-json\/pressbooks\/v2\/chapter-type?post=46"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-json\/wp\/v2\/contributor?post=46"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.palni.org\/spcleanmanufacturing\/wp-json\/wp\/v2\/license?post=46"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}