# KPIs with Control Charts

[W. Edwards Deming](https://en.wikipedia.org/wiki/W._Edwards_Deming) popularized the use of [Statistical Process Control](https://en.wikipedia.org/wiki/Statistical_process_control) as a means to improve quality. This method transformed Japanese industry into an industrial power after being completely destroyed after World War II.

opsZero implements Statistical Process Control and we use **Control Charts** to improve our processes as Quality is a part of our Principles.

We have certain goals with our KPIs (Key Performance Indicators):

1. **Conservative** — We want our numbers to reflect reality.
2. **Consistent**— All KPI charts should look the same with a 1 sigma control on both the Upper and Lower Limits.
   
   - Charts should show “up and to the right” for any goal we set up.
   - This makes it easy to see at a glance if we are attaining our goal.
   - To achieve this, we use Control Charts, which track a process over time (average, Upper Control Limit, Lower Control Limit).

Control Limits are based on the **standard deviation**. The aim is to keep the process within its limits and gradually tighten them over time.

- A 3 sigma upper/lower limit may not be effective.
- Reducing variance to bring the average within 1 sigma or even 0.5 sigma may be ideal — depending on the process.

The nice thing about Control Charts is that they can be used for:

- Revenue goals
- Process goals
- Any measurable goal over time

This makes Control Charts a useful visualization across functions.

At opsZero, Control Charts are used for **all at-a-glance KPIs** to find patterns in how we are moving towards our targets. In addition, we use [Pareto Charts](https://en.wikipedia.org/wiki/Pareto_chart) to build products that reduce Support and Sales issues (covered in a future post).

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## Example: Generate Control Charts in Python

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## Videos

How do SPC control charts work? - YouTube

[How do SPC control charts work?](https://www.youtube.com/watch?v=Ugcb7Vlp0Ts) [The Engineering Toolbox Channel](https://www.youtube.com/channel/UCX-H7IOnCfHihvtnypTORMA)

SPC Control Charting Rules - YouTube

[SPC Control Charting Rules](https://www.youtube.com/watch?v=JaBJD7ocVq4) [The Engineering Toolbox Channel](https://www.youtube.com/channel/UCX-H7IOnCfHihvtnypTORMA)