Featured Flashcards 2024 H2
Subscribers to the weekly Entropic Thoughts newsletter know that in every newsletter, I share one interesting flashcard from the past week. The newsletter has now run for six months, and this is a compilation of the flashcards that have been selected, for the benefit of non-subscribers.
Flashcards by category
These are probably not interesting to read top to bottom, but instead pick a category you think you know a lot about, read the question, and see if you can come up with an answer before looking at the answer written here.
Many of the answers here will seem nonsensical out of context. I get most of the context from the other 20 flashcards that I created along with each of these, but I have tried writing some of it down also – and you’ll find it in the newsletter archives.
Innovation
Cutting-edge innovation projects tend to come with lessons that can be applied also to more mundane projects of software product development. But that takes remembering these lessons, and doing so is easier when one also remembers some context around each historic project.
- What was the precursor to the oil drop experiment, and why did it fail?1 The water drop experiment, which failed because water evaporated.
- Who showed humans express confidence in log–odds?2 Peirce and Jastrow.
- What does agc stand for?3 Apollo Guidance Computer.
- What did the fuzzy specifications for the AGC result in?4 The software engineers did a bunch of the early mission planning in order to find out what code they actually needed to write.
Product development
Many things I flashcard touch on product development, but this category pertains things I learn from books that are specifically about product development.
- Before answering a question, what should one consider?5 Does answering this question here and now generate reusable knowledge in a cost-effective way?
- What is a common thing people want in an mvp that is not necessary?6 Self-serve sign-up.
- Why should you spend time to understand the problem being solved, rather than just accept requirements?7 People solutionise.
Making software
Similar to the category above, many things I flashcard are meant to help me improve at making software, but these are specifically about software.
- What do experienced programmers do during code review that seems to allow them to find more faults?8 They spend more time on the initial scan of the code, where they build a mental map of the code to be reviewed.
- How can one describe distributed systems?9 The defining characteristic of distributed systems is failure.
- Which fold is foldr, and which is foldl?10
foldr = f x (foldr f e xs)whereasfoldl = foldl f (f e x) xs. - How can we describe congestion?11 The location where excess demand is being stored.
Fermi estimate food
I have a few flashcards that are about pure numeric data points, which serve to help me make Fermi estimates on various things. These are rough, order-of-magnitude numbers that one has to memorise because they are hard to work out from other, more basic facts.
- What was the space shuttle’s actual frequency of loss of crew during its operating years?12 1 in 67.
- How many micromorts is a day in the life of a 90-year old?13 500 micromorts.
- How many lines of code was the original Doom?14 40,000
- How many days are there in a Gregorian year?15 365.2425
Professional practices
I sometimes read about what other professionals do because (a) I like variation, and (b) it’s always interesting to try to map concepts from other domains onto mine, and see what can be learned from that. Often not much, but sometimes very useful things few people think of because they’re out-of-domain.
- (Firefighting) How wide should a fireline be?16 A fireline should be about 2.5 metres wide.
- (Consulting) What is an economic drawback of hourly billing?17 You are limited to charging, at best, as much as you have time available.
- (Military) What is the effect of surprise?18 Surprise delays reaction.
- (Learning) What are the six basic signs of expertise used in applied cognitive task analysis?19 Past and future, big picture, noticing, job smarts, opportunity/improvising, self-monitoring
- (Poker) When you have a good hand you should almost always bet, except in which two circumstances?20 You should not bet when the pot is tiny and/or your hand is and will remain the nuts.
- (Bureaucracy) Which parts of work become emphasised in an auditable organisation?21 The parts that represent themselves well in spreadsheets.
- (Statistics) Where was the threshold set at for batches of 100 coins at the trial of the Pyx?22 Hundred times a single coin, i.e. 20 standard deviations away.
There are explanations published for each
You can check the newsletter archives for more information on each of the flashcards above. For example, the question about humans assessing confidence in log-odds comes from an article by Peirce and Jastrow called On Small Differences in Sensation. Here’s the additional context newsletter readers received:
At the time the article was published, there was a popular hypothesis that human senses had a lower threshold, beyond which differences can no longer be perceived. Peirce and Jastrow dispense of this hypothesis through an extremely careful experimental setup, where they attempt to judge differences in pressures placed on their fingertips. They find no threshold – it’s a smooth function of discriminatory ability all the way down.
However, to get more vivid data, they also recorded their confidence in their reported difference sensation on a numeric scale from 0 (meaning “wild guess”) to 3 (meaning “virtual certainty”).
They noticed that this confidence indication was roughly proportional to log[p/(1-p)], where p was the probability of guessing correctly. Isn’t that kind of cool? This was essentially what I was aiming for in the sidenote where I suggested switching to a different propensity scale to treat (some) overconfidence.
(Something else interesting about their experiment was that even when they indicate zero confidence, they are right slightly more often than not. They suggest that maybe somehow the body is capable of detecting finer differences than are surfaced at the level of conscious expression.)
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