Sandi Toksvig ponders power in numbers

Being of small stature, I’m not too keen on a crowd. The word itself comes from the Old English “cruden” meaning “to press” or “to crush”, and being pressed or crushed into a taller person’s armpit is low on my list of fun things to do. Lately, however, the crowd has become de rigueur for anyone thinking the world is being run with anything less than perfect skill. There have been chanting crowds in Tahrir Square, camping crowds at St Paul’s and decamped crowds on Wall Street. Protest, however, is not the only arena where the crowd is becoming king.

In these days of the great inter-web, many a problem is solved through “crowd sourcing”, in which a tricky issue such as a design challenge is broadcast to an unknown group of solvers. This “crowd” is usually made up of people (geeks) who dwell in online communities, which are just like regular communities but without the social life. They apply their amateur expertise to help find the answer or to select the best solution from other people’s answers. They do this for free and in lieu of having anything better to do.

It is, of course, nothing new. My favourite statistician (not something everyone can claim to have), Sir Francis Galton, understood the concept of the “wisdom of crowds” as far back as 1906. He was visiting a country fair when he came upon a “Guess the weight of the dead ox” competition. The correct answer was 1,198lb. Not one of the nearly 800 people who had a go got it right, but if you worked out the mean of all their guesses it came to 1,197lb, which is pretty close.

Galton is an interesting fellow but he had some fairly serious blind spots of intelligence. He once travelled round Africa attempting to analyse “the measurement of black African ladies’ bottoms” and tried to use statistics to determine the distribution of attractive people in England. It would take quite a crowd to guess how he might have celebrated the founding on this day in 1839 of the American Statistical Association. Indeed, not only celebrated but perhaps sat down to calculate the probability that it might have been founded on some other day.

The word “statistic” originally related only to data about the state. These were figures invented to allow any government of any day to bamboozle the poor public into thinking all is right with the world. This month, for example, the Home Office produced many fine figures about drug seizures. Depending on who was explaining the results, the number of drugs hauled had either gone up brilliantly (the Home Office version) or declined rather badly (the Not at Home at the Moment Office version), thus leaving most of us none the wiser.

Personally I am not a fan of such data, always recalling the adage that “There are three kinds of lies – lies, damned lies and statistics.” But I do like people who can use maths to work out probabilities and help with practical problems. There is a chap at the University of Tokyo called Daichi Yanagisawa, who has used pencil and paper to work out the best way to get a crowd through a narrow opening, and the answer is rather surprising – put a pillar in the way. He timed a crowd of 50 women as they exited as quickly as possible through a door. Then he tried it again but this time with an eight-inch-wide pillar placed two feet in front of the left side of the exit. The result was that an extra seven people passed through the door per minute. (I could tell you that that’s 2.8 people per second instead of 2.92 but I have a problem with .8 of a person.) The pillar stops the area right in front of the door becoming too crowded. There is less pushing and shoving and everyone can egress more quickly.

Anyway, I mention all this because I am joining a crowd. The splendid river ferry which I take to work along the Thames is to cease running because, despite being very busy, someone says the maths doesn’t work. The commuter folk on this riverine service are planning to protest. They’re a cheerful crowd and I am confident there will be no pushing or shoving. I think it is important to be part of this peaceful campaign, but I may still check to see if there is a pillar near the door when we meet.

The Telegraph

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