> for thermostat B there are many more outliers. We’d say that [...] thermostat B is not [under statistical process control]. (In practice, you’d draw a control chart to identify whether the system is under statistical control).

I did draw the control chart, and thermostat B is definitely under statistical process control: https://xkqr.org/info/xmr.html?baseline=33,97,41,65,72,71,64...

To be clear, this is not a diss of the article. It is hard to create fake data that look realistic at first glance but are not under statistical process control. That's just how good control charts are at separating signal from noise.

If someone wants to learn more, this is how I put the introduction: https://entropicthoughts.com/statistical-process-control-a-p...

Eh depends what you mean I suppose, but a small dense cluster with enormous outliers is not a great sign usually.

Almost nothing has (effectively) unbounded variance, so most things are under statistical control in a sense. With some notable exceptions (earthquakes, any other event with exponentially decreasing frequency and exponentially increasing damage).

For the sake of argument I assumed the author meant that the variance of the thermostat was too high to be practical.