How to Use SPC Charts Feature

SPC Charts feature can allow a visual review of historical data.  Even when you do not need to confirm statistical data to control limits, this tool can be helpful to review general trends over time.  The initial data loaded in the SPC chart is generic and care must be taken to apply filters for customer ID and tank ID prior to data review.  This tutorial will explain various available graphing, filtering and review options available for SPC Charts Feature.

1. Find Sample

Follow steps described in the "How to Search in LIMS" tutorial to search and drill down into the sample which requires trend review.

When reviewing historical data select the most recently logged sample.  This is because SPC chart is time based and will show you data preceding the sample from which you opened the chart.  When you open the chart from an older sample there might be more recent samples that have been logged which will not show on the chart.

2. Select a Parameter to Review

  1. Click on the checkbox next to the parameter requiring trend review
  2. Click on SPC chart icon

Clicking on the chart icon without selecting a parameter will not open the charting window.  When review is required for all parameters, click to select the top parameter which will open the charting window where you can change between parameters.

3. Chart Window Overview

3.1. Chart Section

  1. Toolbox panel
    1. Refresh button: when applying filters, changing parameters... press this button to refresh the chart
    2. Expand Chart button: hides statistical window, and expands the graph
    3. Print chart button: allows to print just the chart portion of this window
    4. Export data to excel: Provides an excel export of Numerical Results and associated sample ID's
    5. Export to XML: Provides an xml export of Numerical Results and associated Sample IDs
    6. Exports as a Picture: Provides an export of the chart in .jpg format
    7. Save: When samples are dropped from the chart, press save button to capture changes
  2. Numerical Results Scale
  3. Sample ID (Note: Sample ID is assigned by the system automatically using the date on which sample is entered into LIMS, thus sample ID is an indirect scale for entered on date)
  4. Statistical information: This info changes based on what you have selected in "Statistical Options" section
  5. Allows to Drop a result from SPC chart when special cause for variation is assigned, or there is a known reason of why sample does not represent normal operating conditions. (more details in section 4)
  6. Allows to Drill down to a selected sample (more details in section 6)

3.2. Histogram Section

  1. Click to expand Histogram Section
  2. Shows a histogram of the data

3.3. Statistical Options Section

  1. Click to expand Statistical Options Section
  2. Click the checkbox next to each choice to show on the chart.
  • Show Average: When this option is selected the chart will show a line for the average of data points on the chart
  • Show Limit 1: When this option is selected the chart will show lines that represent the Internal Low and High for that parameter.
  • Show Limit 2: When this option is selected the chart will show lines that represent the TDS Low and High for that parameter.
  • Show Limit 3: When this option is selected the chart will show lines that represent the 3rd set of limits (not usually used)
  • Show Sigma 1: When this option is selected the chart will show Mean +/- 1 Sigma Control Limits
  • Show Sigma 2: When this option is selected the chart will show Mean +/- 2 Sigma Control Limits
  • Show Sigma 3: When this option is selected the chart will show Mean +/- 3 Sigma Control Limits
  • Show Target Value: When this option is selected the chart will show the line for target value if one is set-up for this parameter
  • Show Moving Range: When this option is selected the chart will show both the individual data plot and a moving range plot in the chart section
  • Show Dropped: When this option is selected the chart will show points which were previously dropped
  • Show Legends: When this option is selected the chart will show a legend describing the lines on the chart as well as some key statistics such as Max, Min, Avg, Median, Sigma, number of points used and number of points dropped.
  • Maximize Scale: When this option is selected the chart will expand the y-axis using the min and the max for the scale.
  • Show Grid: When this option is selected the chart will apply gridlines to the chart
  • Show Fixed Limits: When a process code has fixed control limits the chart will show them.  If a process code does not have fixed control limits you will see an error: Sample Type does not have fixed limits defined for this parameter
  • Show Values: When this option is selected the chart will show numerical values associated with each data point.
  • Show PCT Recovery: This is a specific measure kept in LIMS for a feature that we do not use.
  • Show CL: When this option is selected the chart will show Control Limits as calculated using the "within standard deviation" -> calculation method used in minitab for control limits.

3.4. Sample Filters Section

  • Process Code: Shows the process code that was assigned to sample from which you opened the chart.
  • Customer #: Can be used to set customer # specific filter
  • Logged On: Can be sued to set Sample Entered On date filter
  • Tank ID: Can be used to set up TankID specific filter.  Can only be set after customer # is defined because tanks are process and customer number specific
  • Customer # Spec: Can be used to set filter based on customer specific template of the process code
  • Sampled On: Can be used to set filter based on date when sample was sampled out of the bath
  • STARTDATE and ENDDATE: Fields are used together to define a time frame for a trend chart
  • LASTN: field is used to define how many points to show on the SPC chart
  • RESULT_STATUS: DO NOT USE - leave as default
  • CustomerID_Option: DO NOT USE - leave as default

After filters are set.  Click the refresh button from Chart Section to see the updated chart.

3.5. Parameter Filter Section

  1. Click to expand the section
  2. Select the parameter to show in the chart section.
  3. Select check box to show Print Flag 1 Parameters and Un select checkbox to show all parameters

After parameter selection is changed.  Click the refresh button from Chart Section to see the updated chart.

4. How to Drop a Sample from SPC Chart

Dropping a point form SPC Chart is done on the sample level.  Even if you're on a specific parameter and you drop a point, this will drop the entire sample data set for all the parameters within this sample.

  1. Click on the point that corresponds to the Sample ID that needs to be dropped to select it.  The selected data point will be black
  2. Enter the Drop Reason into the text box
  3. Click "Drop Sample"
  4. Graph will refresh without the dropped point

4.1. How to Show Points Associated with Dropped Sample on SPC Chart

  1. Expand the "Statistical Options" section
  2. Click on "Show Dropped"
  3. Graph will refresh automatically and show the dropped point with a red diamond

4.2. How to Un-Drop a Sample

  1. Follow steps to Show Dropped Points (Section 4.1)
  2. Click on the Dropped Point (not the text on the button "Drop Sample" changes to "un-Drop Sample"
  3. Click the Undrop Sample Button

5. How to Apply Customer # and Tank ID Filters

  1. Expand Sample Filters section
  2. Type in Customer #, or click on blue Customer # text link to search for the customer number in a pop-up window.  Click "Select" next to the necessary Customer number
  3. Type in Tank ID, or click on the blue Tank ID text link to search for customer specific tanks.  Click "Select" next to the necessary Tank ID
  4. Click Refresh Button to see updated chart

6. How to Drill Down to a Different Sample from SPC Chart

  1. Select the data point on the chart
  2. Click "Drill to Sample" button

7. Exit SPC Chart Window

Chart is opened as a new pop-up window.  To return to your sample simply click the "x" button to close the window and return to your sample.

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