Sunday, 30 January 2011

Numerical illiteracy

I had a look at our free local newspaper, the Birmingham Mail Extra. In this issue is an article titled "Suburb is now crime hotspot". This article has several problems, which are indicative of the problems of representing what happens 'out there' in the form of a newspaper article.

Quinton had very little burglaries, "averaging just one or two burglaries a month" over the last nine years. But now, crime has "shot up by 29%", more than the rest of Birmingham where crime only rose by 21%.

I find this rather misleading, and I worked through an example with the kids at the dinner table, which illustrates the problem:

Suburb A had 10 burglaries in 2009, and 12 in 2010. That is an increase of 20%.
Suburb B had 4 burglaries in 2009, and 5 in 2010. Increase of 25%.
Suburb C had one burglary in 2009, and two in 2010. A whopping 100% increase.

First lesson: percentage increase is meaningless unless everybody started in the same place. Why do developing economies have higher growth rates than Europe and the US? Because the percentage looks bigger. If you double your output from 100 cars to 200 cars you increase by 100%, but to maintain that rate you will have to produce an additional 200 cars the year after, and then 400, 800 etc.

Second lesson: without a fixed reference point (such as burglaries per 1000 inhabitants) you have no idea whether the risk of your house being burgled is high or low. Everything is relative, but you still need a fixed point to evaluate things.

Third lesson: this is not mentioned, but is that difference between 29% and 21% statistically significant? With "one or two burglaries a month", the variation seems rather high, given those small numbers. So if there was one extra or one fewer burglaries, how would the 29% change?

Final lesson: be careful with calling places "crime hotspot" when your statistics are that shaky.

Now I don't expect a staff reporter at the Birmingham Mail to apply the same rigour as a scientist (or any other, non-science researcher), but the way the article is presented is simply misleading. To me this sounds like a scare story being created out of some random statistics. I don't know whether that is the case, and maybe Quinton is really a crime-ridden area, but I cannot tell from the few facts given to me in the article. The reason for this development given in the paper is that there are now 5 fewer policemen covering Quinton. Is there really such a cast-iron correlation between policemen and crime rate? How about the influence of the recession on crime?

I now have more questions and know less than I did before reading that article!

Wednesday, 12 January 2011

The cuts start now...

My two elder daughters (who are at primary school) are currently getting free language tuition at a nearby secondary school. That school has specialist status for languages, and provides those additional classes for free as an after-school activity for the younger ones. Apart from teaching the kids Spanish/French/German/... I guess they also benefit themselves through advertising their school. No idea how much the kids actually learn, but it is a fun class, they enjoy it, and if they can speak a few French phrases in addition then that's great. It definitely gets them interested in foreign languages, and that is a bonus given the current attitude to those in England.

However, we yesterday got a letter from the school. The new coalition government has abolished the 'specialist status' scheme, and presumably that means that any funding that was connected to this status is going to disappear. From April onwards, the letter states, the school cannot afford to provide those additional language classes any longer.

This, of course, is not the school's fault. But it is really sad that foreign language classes for primary school kids are disappearing, and it shows that this government got its priorities wrong. I'm not too worried about my own kids, as they get a lot of exposure to other languages, but children from mono-lingual families are now losing out. Not all parents can afford to pay for language classes provided by, eg, Club Fran├žais, after school.

In my view, learning foreign languages is vital in the modern global world. Even though many people learn English as a second language it severely limits you if you can only speak one language. And since modern languages are no longer compulsory at A-level, recruitment for modern language departments at English universities has gone down.

Given that the British economy has little manufacturing left, languages are vital if we want to compete on the global market. Cutting down spending in education is the wrong way to move forward. But this cabinet of millionaires does seem to have other priorities.