SPC Box Plot

Visualize process data distributions as box plots with built-in Statistical Process Control — right inside Grafana. SPC Box Plot groups your measurements into subgroups, draws standard box-and-whisker plots, and overlays robust Xf-Rf control limits so you can detect shifts in process spread and location at a glance.

Why SPC Box Plot?

Control charts tell you when your process changes. Box plots tell you how the distribution changes — median, spread, quartiles, and outliers all in one view. Combine them and you get both.

• Resistant control limits — the Xf-Rf method (Peixoto 2003) uses the middle half of each subgroup, so a few outliers cannot skew your limits
• Three input modes — works with raw time series data, categorically grouped observations, or pre-computed box statistics from your database
• Outlier visibility — individual points beyond 1.5 × IQR are plotted separately so they never disappear into the box
• Capability at a glance — add LSL/USL lines and the statistics table automatically shows Cp, Cpk, Pp, and Ppk for every subgroup

Features

Feature	Description
Box-and-whisker plots	Q1/Q3 box, median line, whiskers (1.5 × IQR), individual outlier points
Mean marker	Optional marker at the subgroup mean
Xf-Rf SPC	Robust control limits using resistant estimators (Peixoto 1992/2003)
Three data modes	Auto-detects time series, categorical, or pre-computed input
Control lines	LCL, UCL, Mean, Min, Max, Range, LSL, USL, Custom, Nominal
Fill regions	Shade areas between control lines to highlight process zones
Statistics table	n, Mean, Std Dev, Min, Max, Q1, Median, Q3, IQR, Cp, Cpk, Pp, Ppk
Resizable layout	Drag the splitter between chart and statistics table
Dashboard variables	subgroupsize variable to control all panels from one dropdown

Getting Started

1. Install from the Grafana Plugin Catalog.
2. Add a panel and select SPC Box Plot.
3. Connect any data source returning numeric time series data.
4. Enable SPC in the panel options and set your subgroup size (4–15).
5. Add LCL and UCL control lines to see the process control zone.
6. Add LSL and USL lines to enable capability index calculations.

Documentation

For the complete feature reference — all panel options, data mode schemas, Xf-Rf formulas, capability index definitions, and dashboard variable configuration — see the full documentation.

Part of the KensoBI SPC Suite

SPC Chart Panel — XmR, Xbar-R, and Xbar-S control charts for monitoring process stability over time.

SPC Histogram Panel — Distribution analysis with histograms, bell curves, and capability indices.

SPC Pareto Panel — Identify the most significant contributors to defects or downtime.

SPC CAD Panel — Bind SPC data to 3D part geometry for visual quality inspection.

SPC Characteristic Datasource — The datasource that powers the SPC CAD panel. Connects to your measurement database (PostgreSQL or MSSQL), lets you select features and characteristics through a point-and-click interface, and returns SPC statistics, time series measurements, and forecast data - no SQL required.

License

This software is distributed under the Kenso Software Commercial License. Use requires a valid commercial license. No open-source rights are granted.

Getting Help

• Contact support at https://kensobi.com/contact
• KensoBI Discord