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From Furious of Feltham
One of this evening's news headlines is a story about a mother whose conviction for the murder of her children was overturned. As a result of this, the BBC website produced a page commenting on the suitability of one of the witnesses, namely Sir Roy Meadow.
Now, Sir Roy belongs to a class of people who really annoy me. Being responsible for convicting an innocent woman ? No (well, actually yes, but not specifically what I'm complaining about). It is because he is a non-statistician claiming to be an expert on statistics.
This happens... far, far too often. Doctors are particularly guilty of it because the use of their own data in the field of medical statistics makes a vocal minority think they know how to interpret all the results. But the lack of statistical training really, really shows. And it gives those of us who actually work in the field a bad name.
Grrrrr.
Now, Sir Roy belongs to a class of people who really annoy me. Being responsible for convicting an innocent woman ? No (well, actually yes, but not specifically what I'm complaining about). It is because he is a non-statistician claiming to be an expert on statistics.
This happens... far, far too often. Doctors are particularly guilty of it because the use of their own data in the field of medical statistics makes a vocal minority think they know how to interpret all the results. But the lack of statistical training really, really shows. And it gives those of us who actually work in the field a bad name.
Grrrrr.
no subject
(small rant follows, not to be taken the wrong way; I'm just trying to explain that it's frustrating when all "doctors" get lumped with the same brush)
I am in no way defending the deliberate misuse of emotive "statistics" that appears to have occurred in this case. However, I am constantly told that my professional duty lies in providing information to enable patients to make "an informed choice". I am very often asked for figures by my punters to help them decide what they want to do e.g. have an operation, try one particular treatment or another. I would find it really difficult to say "I can't give you the mortality rate for this operation unless I can first explain to you the full data that gave rise to this mortality rate, the number and premorbid condition of the patients involved in obtaining the figures, the confidence intervals of the actual result, and the applicability of this figure to your good self". Quite aside from the fact that many people would drift off before the end of the sentence, how can I be expected to convey such complicated concepts in ten minutes?
Answer; I can't ; and neither can most doctors. The patient asking me doesn't want to understand detailed statistics; they want a rough chance in terms they can understand.
Here is a real example, based on what I'd tell a patient with an 8cm aortic aneurism who was otherwise fairly well, and asked advice on whether he should get it repaired or not:
OK, There is a 9 in 10 chance that if your aneurism bursts, it will kill you. If we try to fix it by replacing the damaged artery with a graft, the operation has a 1 in 10 chance of killing you. However, this means that 9 in 10 people do get better after the operation. What you have to balance is whether you prefer to just wait and see what happens knowing that you could have up to 40 years of health before the aneurism bursts (but it mught be less than that, and no-one can predict how much less) , or you can take the 1 in ten risk of an operation, and if it does work then you won't have an aneurism to burst anymore. Have a think about it, talk to your wife, talk to a friend and come and see me again next week.
Does that sound too complicated?
no subject
<grin>
I appreciate that it ain't just statisticians that get annoyed at Sir Roy. Obviously other doctors do too.
I am in no way defending the deliberate misuse of emotive "statistics" that appears to have occurred in this case.
Unfortunately this wasn't the issue. It wasn't a deliberate misuse of emotive stats, but simply that he didn't know his a*se from his elbow when it came to calculating probabilities. What he did was to say that something had a vanishingly small chance of being the case when it was actually pretty large. I.e. suggesting that a accidental death was 1 in several million when it was actually a large two digit percentage.
A little like him telling the patient of your example that they had a 1 in 1,000,000 chance of dying if their aneurism burst when the actual figure was 9 in 10 - to compare on a rough scale.
I am very often asked for figures by my punters to help them decide what they want to do e.g. have an operation, try one particular treatment or another.
And you have my sympathy. Nor would I be annoyed at a doctor who got his figures wrong in this instance.
What I'm cross about is this Sir Roy has taken the stand for a number of serious court cases (murder, for god's sakes) not to give medical evidence (for which he is qualified) but to give wrong statistics.
no subject
Did you have to start a discussion on the misuse of statistics and expert testimony a day before my Torts exam?
Trust me, my frustration mirrors your own. Indeed, it is growing to immense proportions, and may dwarf the sun soon...
no subject