4 ms·

Always worth mentioning: the fact that most people think of themselves as above-average drivers is not a delusion; it happens to be true given quite reasonable

• eragnew 14y ago
  Exactly! Many people seem to have a lot of trouble with what the word 'average' means. It depends on the context!
  • lloeki 14y ago
    The 'average' meaning does not depends on context but: - on the distribution - on whether by 'average' you mean 'mean' (in statistics, arithmetic mean) or 'median' (what value cuts the population in half) The GP gives an example of people being above average by having two legs. I will take a similar example but in a classroom. Say students in a classroom take a test scored from 0 (worst) to 20 (best). The result of the test is as follows: forty students get a 11 and ten gets a 1. That makes a mean of (11x40+10)/50 => 9. Hence all forty students are above average. If we plot the number of people per mark this gives a very special (and artificial) distribution since we made it up to make the point that it is possible for most people to be above average. In more realistic scenarios and unless skewed by external factors (bad test, wrong population, cheating) the distribution is often close to being normal, i.e mean and median are approximately the same (hence it's an impossibility to have 80% of people above mean). Yet what's really interesting in Dunning-Kruger tests is not the actual results of the tests, it is the comparison between one's own assessment and real results, which actually abstracts from distribution problems and 'average' discussions, since each one person is compared to oneself. In the above whacky scenario we could have expected people getting a 1 to evaluate themselves scoring a 8. If you don't want to read the whole paper, just look at the quartile/percentile graphs in the paper. They speak for themselves.
    • Retric 14y ago
      When the vast majority of people fall into the 60-100 range, but it's still possible to get zero's (ex: cheating) you don't end up with a normal distribution. This is one of the reasons most standardized tests give percentile results. IMO, the Dunning-Kruger effect relates to this. Compared to people that regularly ride horses I am probably at the bottom 5 percentile. However, I am better than most people because most people have never ridden a horse. As people improve the list of people they compare themselves to shrinks faster than their skills improve. Being the worst player in the MBA makes you better than 99.99999% of people, but that does not let you keep your job.
    • anthonyb 14y ago
      The distribution is the context of an average. Also, your example makes exactly the same point as the number of legs one, but is much harder to understand. I'm not sure why you used it.
• gdacuna 14y ago
  The article talks about the measurement of skill. The number of accidents that a driver has caused in the past year is not a good measurement of skill. Essentially the difference you bring up is whether something can be expected to fit a normal distribution (where the average is by definition in the middle). It's a reasonable assumption that skill will fit a normal distribution, but the number of accidents caused in the past year is much more likely to fit a Poisson distribution.
• sophacles 14y ago
  But see, these aren't even reasonable measures. In the case of legs, there is a hard upper bound which changes the useful definition of average away from the mean. This is a fairly intuitive thing. Similarly with driving, a terrible measure is number of accidents per year/number of drivers that year. It just makes no sense, because it doesn't take into account the person's entire driving record. An intuitive measure might be how many accidents that person has been in total compared to the average number of accidents a driver has been in (of course, this makes people who have been hit by someone blowing a stop sign bad drivers, even though they had no major input to the accident... again intuitive, having this conversation with someone not well versed in stats will have this exception outed pretty quickly). Basically both of these measures being considered reasonable suggests people who think this don't really have the wherewithal (knowledge or expertise) of legs or accidents to properly assess what makes sense.
  • glenra 14y ago
    Whether or not you take into account the entire driving record (which you arguably should not since people's driving ability changes over time), another relevant fact is that some people are unusually bad drivers - causing lots and lots of accidents or near-accidents all the time. The few drivers who are actively a menace to everyone else make the rest of us look good by comparison. There's an upper limit on how good a driver you can be and most drivers aren't terribly far from that limit - they know their abilities and drive within them most of the time. But there's no strong lower limit on how bad a driver you can be. So we all grok intuitively that a few people who are drunk, high, angry, near-blind, aggressive or just terribly lacking in judgement are way over there on the other side of the driving-well scale from us; that makes us "above average drivers".
    • sophacles 14y ago
      Actually by your argument, there is a strong upper bound. Therefore, by basic statistics reasoning, the mean is no longer a remotely valid measure of "average" - mode is much better in this case. Therefore average still constitutes most people. If you strictly are defining "average" to be mean, then sure, everyone is an above mean driver, however if you take average to be defined in a way statistically relevant, then it means "the measure of population that encompasses most of the population - the typical value of the population". (hint, if it is the typical value, most people can't be better than typical, it is definitionally impossible). Basically, I'm taking the long way of telling you to stop being disingenuous if you want to make an argument.
• VMG 14y ago
  Most people might be better than the average driver, but not better than the typical (median) driver (same goes for legs). I'd say that the typical is a better reference point than the average, since the counter-intuitive effects you describe disappear, and the reference point "1,9999995 legs / person" is pretty useless.
  • gosub 14y ago
    Wouldn't the typical driver be the mode, not the median?
    • lindenr 14y ago
      I'd say it depends. Even "average" can be several different things depending on your definitions. More precise than "average" is "mean", and even better than that is the "arithmetic mean". Typical is typical in its ability to be misunderstood.
    • pcopley 14y ago
      I think in the example above he means mode in that people have 2 legs more often than they have any other number of legs.
  • dredmorbius 14y ago
    "Average" is a term which can be claimed by the arithmetic mean (the word you're confusing it with), the median (midpoint value), or mode (most frequently occurring value).
• saraid216 14y ago
  It's also "quite reasonable" to correct for outliers like those who cause accidents. If you drop those people off your dataset, then your distribution is a flat line because it's too lacking in nuance to describe anything useful.