Tuesday, 23 July 2013

Overripe cherries

The real forbidden fruit - don't pick me!
In science, one of the worst sins is cherry picking. I don't mean it's a bad move for scientists to get themselves some of the fleshy drupes of Prunus avium. They are delicious. The cherry picking in question refers to picking out bits of data that support your hypothesis and ignoring the rest.

A really bad example of cherry picking would be something like an experiment to measure the wibblability of cheese strings. (I can't be bothered to think up a real experiment.) Let's say they are expected to have a wibblability of 12 on the Kraft scale. A series of measurements come up as 8, 12, 7, 7, 13, 6, 8. Not encouraging... unless you only report data points 2 and 5. Naughty - but it happens. It doesn't have to be as explicit as that, though.

Let's imagine you are doing a psychology test that requires considerable concentration. Half way through there is a loud bang in the street. Everyone rushes to the window to see what happened. After a little while they get back to the test and continue. Let's say the current theory suggests outcome A for the test, but it could also have outcome B. So the psychos (sorry, psychologists) mark the test and they get outcome A. Clearly the incident didn't disrupt the test, so they record the data. But now imagine on marking the test they got outcome B. That wasn't expected. So it was probably the disruption that invalidated the test, because the subjects lost concentration. So they discard the data. See what they did then? Subtle cherry picking - keeping data that supported the theory, throwing away data that didn't - but it didn't seem so bad, because they had an excuse.

In politics, the usual approach is far less subtle. Politicians cherry pick all the time, presenting data that supports their case, ignoring data that doesn't. Or in the case of UK government advisor Professor David Nutt back in 2009, firing the scientist if they don't like the data. We almost expect this with politicians - but why? They shouldn't be allowed to get away with it.

However, I would say that we are much more tolerant of cherry picking when it is employed by activists and charities, and we shouldn't be. I'm afraid they too resort to cherry picking, but we tend to just get their message without any attempt to see whether they are only giving us a part of the data. This is true, for instance, of almost all campaigns for and against different forms of power, whether it's wind power or nuclear. But the example that made me write this post is the anti-globalisation movement.

While most of probably don't support the means sometimes used, many people have a sneaking regard for the message of anti-globalisation. We know those big companies (and especially banks) are rapacious uncaring monsters. And some certainly are. We know that poor people in third world countries are being exploited so we can get cheap clothes and electronics and so on. And they are. This is important stuff that needs consideration. However, I really don't think the anti-globalisation people do themselves any favours by the rampant cherry picking they employ. The picture is more complicated.

I'm currently reading a book on the global crisis by the excellent (if sometimes strangely intoning) Robert Peston, the BBC's business editor. (I'll be reviewing it when I've finished.) And he points out what a huge benefit globalisation has been to many, many millions of poor people. The fact is that living standards in the likes of China and India have been improved on a massive scale by globalisation. Frankly most of the population in places that are on the 'sweatshop' end of globalisation had totally terrible lives beforehand. Now what we mustn't do is cherry pick in the opposite direction. There are still those bad sides of globalisation. But what this says to me is that globalisation is not a bad thing - it does a vast amount of good - but that we need to do it better.

This is a message those protestors really ought to learn. Otherwise what they are campaigning for is put over a billion people back into intense poverty. And that's not really what they have in mind, I think.

Image from Wikipedia

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