SPC Chart & Calculation Options

With the data settings, the key settings used to display the SPC chart can be modified.

Chart Type

The SPC visual is set to individual measurements (i) charts by default, also known as XmR charts. There are other options available which use an assumed probability model to compute the 3-sigma limits. See the documentation on Chart Types for further details on each type.

Keep Outliers in Limit Calcs.

By default (off), unusually large moving ranges are dropped before the limits are calculated, so that a single extreme point doesn’t widen the limits. A moving range counts as unusually large when it is at least 3.267 times the average moving range (3.865 times the median moving range for i_mm charts). Turning this option on keeps them. It applies to the i, i_m, i_mm, t, p prime and u prime charts.

Multiplier

The multiplier affects the scale of the final value that is displayed in the SPC chart, with the default set to 1 for every chart type. For p and p prime charts, Report as percentage (Automatic by default) shows a multiplier of 1 as a percentage, multiplying by 100.

Decimals to Report

Sets the number of decimal places reported in the y-axis, tooltips and values written on lines. The number of decimal places in the y-axis can be overridden by Tick Decimal Places in the Axis group of the Y-Axis Settings.

Report as percentage

A drop down box to set whether the value should be reported as a percentage. This setting has three options:

• When set to Automatic, the chart will report as percentage when a p or p prime chart type is selected, with a multiplier of 1 or 100.
• When set to Yes, the chart will always report as percentage, multiplying by 100 in place of the Multiplier.
• When set to No, the chart will not report as percentage.

The conditional formatting follows the same values as the drop down box.

Split Limits on Click

The split limits on click toggle allows users to click on multiple points in the SPC to recalculate the control limits for all the points before and including the clicked point, and all the points after the clicked point.

An example of this is below:

Developers are also able to toggle on the ability to split limits, set the location of your split limits, then toggle off the feature. This is useful when there is a clear process change and the limits need to be reset, but the functionality to split limits does not need to be carried into the published dashboard.

To reconcile the split limits, click on the same point that was initially clicked to split the limits (the last point in the limit series).

Truncate Lower and Upper Limits at

The lower and upper limits are able to be truncated using this setting, which sets a minimum and a maximum for the limits.

A use case for this would be in the example above for split limits, where the lower control limit is below 0 and into the negatives. Although theoretically possible using the i-chart probability model, practically this may not make sense for your measure if negative values are not possible. The lower control limit may be truncated to zero by setting this option:

All Settings

Data Settings

Setting	Description	Default	Values
Chart Type	Type of control chart; see Chart Types for the inputs each needs.	i - Individual Measurements	• run - Run Chart (run) • i - Individual Measurements (i) • i_m - Individual Measurements: Median centerline (i_m) • i_mm - Individual Measurements: Median centerline, Median MR Limits (i_mm) • mr - Moving Range of Individual Measurements (mr) • p - Proportions (p) • p prime - Proportions: Large-Sample Corrected (pp) • u - Rates (u) • u prime - Rates: Large-Sample Correction (up) • c - Counts (c) • xbar - Sample Means (xbar) • s - Sample SDs (s) • g - Number of Non-Events Between Events (g) • t - Time Between Events (t)
Keep Outliers in Limit Calcs.	Keeps unusually large moving ranges when calculating limits; off drops them first. Applies to i, i_m, i_mm, t, p prime and u prime charts.	Off	On or Off
Multiplier	Multiplies plotted values and limits, e.g. 1000 for a rate per 1,000.	1	Number, above 0
Decimals to Report:	Decimal places for values in tooltips, line labels and the y-axis, unless the y-axis sets its own.	2	Whole number from 0 to 20
Report as percentage	Yes multiplies by 100 and adds a % sign, replacing the multiplier. Automatic does this for proportion charts with a multiplier of 1 or 100. No never adds a % sign.	Automatic	• Automatic • Yes • No
Split Limits on Click	Clicking a point ends a limit period there; clicking it again removes the split. Splits stay when this is turned off, and are ignored when Grouping (Summary Table) is used.	Off	On or Off
Subset Number of Points for Limit Calculations	Calculates the first period’s limits from only this many points; blank or out of range uses them all.	(blank)	Whole number, at least 1
Subset Points From	Whether the subset is taken from the start or end of the period.	Start	• Start • End
Subset Points After Each Re-Baseline	Applies the subset to every rebaseline period, not only the first.	Off	On or Off
Show Date in Tooltip	Shows the date, or the point number for g and t charts, in the tooltip.	On	On or Off
Date Tooltip Label	Name for the date in the tooltip; Automatic uses Date, or Event for g and t charts.	Automatic	Text
Show Numerator in Tooltip	Shows the numerator in the tooltip, when one is supplied.	On	On or Off
Numerator Tooltip Label	Name for the numerator in the tooltip.	Numerator	Text
Show Denominator in Tooltip	Shows the denominator in the tooltip, when one is supplied.	On	On or Off
Denominator Tooltip Label	Name for the denominator in the tooltip.	Denominator	Text
Show Value in Tooltip	Shows the plotted value in the tooltip.	On	On or Off
Value Tooltip Label	Name for the plotted value in the tooltip; Automatic names it after the chart type.	Automatic	Text
Truncate Lower Limits at:	Limits below this plotted value are drawn at it, and points are flagged against them.	(blank)	Number
Truncate Upper Limits at:	Limits above this plotted value are drawn at it, and points are flagged against them.	(blank)	Number