How Well Do You Estimate?

A random UK blogger has published a quiz asking readers to estimate various numeric values which they may or may not have knowledge of; and has analyzed the resulting answers to determine how well people guess. The first part of the results looks at some specific questions, and the second part takes a look at the quiz overall.

Comments

Guestimate

[unixsavant]

I guestimate that the server will be down for the next 30 minutes +/- 1 day....

/.'ing estimates

[rute_1]

Anyone want to estimate how long before the site gets /.'ed?

Ooops, too late....

Re:Mirrors

[mirko]

Not a mirror but the text which actually comes without the pretty pictures...

1st part

28 August, 2004: The weirdness of crowds

[ Home page | Web log ]

So, many thanks to the thousands of people who have now completed my Estimation Quiz. Special thanks to Michael Williams, who posted a link to del.icio.us, Dave Weeden, Chris Bertram of Crooked Timber, Nick Barlow, Chris Brooke, and many others for linking to the site, including a user of Metafilter -- which link drove most of the traffic. (I was expecting to have to wait months for enough people to complete the thing for the results to be interesting, as with my Political Survey. Instead it took two days. That should probably tell you as much as you need to know about my ability at estimating things.)

So, when I posted the link to the quiz, I said that I had an ulterior motive for building the thing. Michael Williams speculated that my purpose was to,

do something terrifying with the data.

I'm not sure whether the below will actually terrify you, but I'll try my best. (There's quite a lot to say, and some will have to follow tomorrow.)

For those who didn't do the quiz, I'll quote from the description:

How far is it from Edinburgh to Cardiff? When did the English Civil War break out? How long does light from the sun take to reach the Earth? You probably have some idea of the answers to questions like these -- or you could make a guess. But do you know when your guesses are right, and when they're wildly off?

This is a general knowledge quiz which tests you on how well you can answer questions like these -- and whether you know how good your guesses are.

For each question, you will give an answer in the form,

a ± b

a should be your best guess at the answer. b is your idea of roughly how far off your guess might be. If you're absolutely sure of the answer, you can tick ``this is the exact answer''; but if you do, and you are wrong, your score will suffer.

You get points for how good your guess of a is, and whether b was an honest estimate of how wrong you were.

There are no trick questions in this quiz.

The quiz asks for estimates of thirty-one quantities. Most are straight general knowledge questions, for instance,

* [How many] bones [are there] in the adult human body?
* [How many] MPs [were] elected to the House of Commons at the 2001 General Election?
* [What fraction] of the population of the United States [are] below the poverty line?

Others require more specialised knowledge, such as,

* [How many] stars [are there] in the galaxy?
* [What is] the distance from the Earth to the Moon?
* [How long does] light from the Sun [take] to reach the Earth?

And some ask for things which few people are likely to know, but which are very easy to estimate, for instance:

* [How many] plastic carrier (shopping) bags [are] used each year in Australia?
* [How many] petrol stations [were there] in the UK at the end of 2001?

(I hadn't realised that the term `carrier bag' isn't understood to mean a disposable plastic shopping bag outside the UK. I adjusted the wording of the question when I discovered people asking, ``what's a carrier bag?'' In fact the quiz as a whole was rather Anglocentric, basically because I expected it to be answered by this web log's half-dozen readers -- mostly in Britain -- and their friends. The results below incorporate data from about 3,000 responses.)

Note that some of the quantities -- like the three astronomical quantities above -- vary or aren't actually known exactly. More on this later.

So, the first question you might ask is, ``are people actually any good at estimating things?'' The answer is that... it depends.

For some quantities -- especially ones which some respondents actually do know exactly -- the crowd's wisdom isn't bad.

I estimate ...

[drmancini]

that the website will get /. ed you insensitive clod

I estimate...

[jmcmunn]

I estimate I am the first person to attempt a short joke on my estimating abilities.

(I know, repetitive. So what, gimme a break that's kinda the point)