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Please be more careful when interpreting the Stack Overflow Developer Survey

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Re: Please be more careful when interpreting the Stack Overflow Developer Survey

#21
post #20

> We asked respondents to evaluate their own competence, for the specific work they do and years of experience they have, and almost 70% of respondents say they are above average while less than 10% think they are below average. This is statistically unlikely with a sample of over 70,000 developers who answered this question, to put it mildly. I’m seeing a lot of argument about statistics, and very little about the w…

It’s too late to edit, and maybe nobody will see this now, but I wanted to add that the particular question of competence and the majority result strongly reminds me about the story of the Air Force discovering that cockpits designed for the average human size were causing crashes because literally nobody is averaged sized.

Discussed on HN before https://news.ycombinator.com/item?id=11230287

“Before he crunched his numbers, the consensus among his fellow air force researchers was that the vast majority of pilots would be within the average range on most dimensions. After all, these pilots had already been pre-selected because they appeared to be average sized. (If you were, say, six foot seven, you would never have been recruited in the first place.) The scientists also expected that a sizable number of pilots would be within the average range on all 10 dimensions. But even Daniels was stunned when he tabulated the actual number.

“Zero.

“Out of 4,063 pilots, not a single airman fit within the average range on all 10 dimensions. One pilot might have a longer-than-average arm length, but a shorter-than-average leg length. Another pilot might have a big chest but small hips. Even more astonishing, Daniels discovered that if you picked out just three of the ten dimensions of size — say, neck circumference, thigh circumference and wrist circumference — less than 3.5 per cent of pilots would be average sized on all three dimensions. Daniels’s findings were clear and incontrovertible. There was no such thing as an average pilot. If you’ve designed a cockpit to fit the average pilot, you’ve actually designed it to fit no one.”

https://www.thestar.com/news/insight/2016/01/16/when-us-air-...

So to go one step further and make a stronger statement, it’s not just possible for 70% of devs to be above average, it’s statistically likely for 100% of devs to be above average with respect to something they do, relative to some group. It’s so subjective that it’s meaningless, and we can’t really talk about the statistics.

Re: Please be more careful when interpreting the Stack Overflow Developer Survey

#22
post #11

Earlier quoted context omitted.

The key is in how you randomly select the sample from the population. This was the author’s point. Just because you have 90k SO respondents doesn’t mean you can say anything about developers as a population. You can say lots of stuff about SO users. Or maybe developers who use SO. But just because you have lots of responses doesn’t mean you know what developers or jugglers or farmers or whatever population interests…

It's not even a random sample of SO visitors, as the there is, at the very least, self-selection bias.

I agree, although I think it’s more easy to correct for this bias to generalize to all of SO than to all programmers.
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