Memory limits, the north pole is moving, and standard deviations
We learn a systemd trick and some history around the perception of physics. We also think about whether rote memorisation of standard deviations is a useful way to get a sense of variation, and if this in turn leads to better statistical literacy.
I hope your week is going well!
New articles
Limiting Process Memory with systemd-run
systemd-run --scope -p MemoryMax=24G -p MemoryHigh=22G -- "$@" is a shell script that runs a process with limited memory, to avoid it blowing up and the system swap thrashing.
Full article (0–2 minute read): Limiting Process Memory with systemd-run
The Discovery of Magnetic Variation
When people hear about experiments designed to figure out if the fundamental constants of the universe change over time, they react with disbelief. But do you know what else people thought was constant? The location of the north pole. Learn about how we discovered it is not!
Full article (1–4 minute read): The Discovery of Magnetic Variation
Flashcard of the week
I have started to get the sense that statistical literacy means a sense of sizes of variation. Some of this I might have gotten from flashcards of the following style.
What is the standard deviation of a Bernoulli trial with p=0.01?
The description is that of e.g. a lottery with 100 tickets of which only one pays out. The answer is
0.1
I have similar cards asking for p=0.05 (sd=0.2), p=0.1 (std=0.3), p=0.2 (sd=0.4) and any higher p can be approximated with sd=0.5 until we get to p=0.8 on the other side when the variance goes down again.
This can be used also in situations that call for the binomial distribution. If there's a 20 % chance we'll hit a target but we get six chances, then the standard deviation of the number of hits is going to be 0.4 * sqrt(6), which is approximated as 0.4 * exp(log(6)/2) or 0.4 * exp(0.4) or 0.4*2.5 = 1.
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