Control charts (Shewhart charts) plot process measurements over time against statistically calculated control limits — typically the mean ± 3 standard deviations. Points outside the limits or forming non-random patterns signal that the process may be out of statistical control and investigation is needed.

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sample	value
1	10.2
2	9.8
3	10.5
4	11.2
5	9.4
6	13.8
7	10.1
8	9.7
9	10.8
10	6.2

{
  "title": {
    "text": "Manufacturing Defect Rate — SPC Control Chart"
  },
  "data": [
    {
      "sample": 1,
      "value": 10.2,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 2,
      "value": 9.8,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 3,
      "value": 10.5,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 4,
      "value": 11.2,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 5,
      "value": 9.4,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 6,
      "value": 13.8,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 7,
      "value": 10.1,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 8,
      "value": 9.7,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 9,
      "value": 10.8,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 10,
      "value": 6.2,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 11,
      "value": 10.3,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 12,
      "value": 9.9,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 13,
      "value": 11.5,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 14,
      "value": 10,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    },
    {
      "sample": 15,
      "value": 10.4,
      "ucl": 13,
      "lcl": 7,
      "mean": 10
    }
  ],
  "series": [
    {
      "type": "controlchart",
      "xKey": "sample",
      "yKey": "value",
      "uclKey": "ucl",
      "lclKey": "lcl",
      "meanKey": "mean",
      "fill": "#6366f1",
      "stroke": "#4f46e5"
    }
  ],
  "axes": [
    {
      "position": "bottom",
      "title": {
        "text": "Sample Number"
      }
    },
    {
      "position": "left",
      "title": {
        "text": "Defect Rate"
      }
    }
  ]
}

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Manufacturing defect rate plotted against UCL, LCL, and mean control limits with two out-of-control points.

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