80% of our students are above average
In Lake Wobegon all the women are strong, all the men are good looking, and all the children are above average. We laugh because it is impossible for everybody to be above average. It is quite possible, however, for 80% of the population to be above average. Take ten people two of whom die at birth and eight die on their hundredth birthdays. In our sample the average life expectancy is 80, and 80% live longer than average. Even if our two unfortunates live until they are 99, 80% still live longer than average. So for any fraction, p%, other than 0% or 100% it is entirely possible for “p% of the population to be taller /shorter/ fatter / thinner / longer lived / or… than average.”
Professor Chris Triggs came to the department in 1990 from the former DSIR. Chris graduated PhD from Auckland. Chris's current research interests include experimental design, biometrics, and multivariate analysis. See all posts by Chris Triggs »
My favourite one along these lines is that most people have more than the average number of legs.
12 years ago
That’s true but the Illusory superiority effect, where people over-estimate the own abilities relative to others is well known.
To say, “well, it could be true” misses the point. The 80% of drivers that say they are better than average (came up in the stat of the week competition) were being asked to rank themselves out of 100 drivers so the average here is a median, not a mean.
12 years ago
I never got the Lake Wobegon example. It’s simple for all the children of Lake Wobegon to be above average. They all have an IQ of 101 or above. Quite feasible.
People misunderstand IQ. There were headlines a few weeks ago over Emmelyn Roettger who was famous for having an IQ of 135 at age 3. Nothing special about that. IQ is standardised for age (the Q stands for quotient) so 2% of all babies of that age will have an IQ high enough for MENSA.
12 years ago
Bill’s beaten me to it – one of my favourites is that millions of New Zealanders have more than the average number of fingers…
Except for my uncle – who managed to lower the national mean by a fraction when he unintentionally removed a finger with a circular saw.
12 years ago
Would Garrison Keiller start the show with “Lake Woebegone where 2 out of ten people die at birth” This would make his statement about averages correct….
12 years ago