I agree having baseline measurements is essential.

With so many batteries having less than 4 year real world lifetimes, baseline numbers must be of $ value.

I have long suggested that everyone set their tire pressure and then do a steady 60 mph fuel economy test over 60 miles on a mostly level interstate highway on a low wind day.

This baseline is a great help when something seems unhealthy with a vehicle,
despite the limitations of plus/minus 8% varying fuel heat content and decreasing tread depth giving mpg gains.

Here on Moparts there have been valuable past posts about baseline numbers of cylinder compression checks, and cylinder % leakdown.

"what is the base rate?"

Allegedly Nobel Prize winner Kahneman said that is the most important question to ask,
According the the new book:
The Undoing Project, by best selling author Michael Lewis

https://www.amazon.com/Undoing-Project-Friendship-Changed-Minds/dp/0393254593