Posts tagged with Bad Stats

Warning: post contains economics. Some readers may find themselves bored silly. In such cases, Dr No recommends taking a tea-break and returning to the post only when the sense of boredom has completely dissipated.

Economists are keen on a concept known as elasticity. There appear, from Dr No’s primitive researches on the matter, to be a disconcerting number of elasticities in economics. Naturally enough, economists dress all these elasticities up in hieroglyphics, but inspected through the lens of common-sense, economics stands revealed as a study of rubber bands, albeit rubber bands that drive economic activity, but rubber bands nonetheless.

Another voice has been added to the hue and cry for a minimum price for alcohol. Within days of Rubber Duck stepping down from his CMO post, the better to quack his favourite message, NICE, the National Institute for Health, Clinical and Anything Else Anybody Will Pay Us For Excellence, has jumped on the wagon. Voluminous guidance, published earlier this week, recommends a raft of measures that, NICE says, will ‘significantly decrease alcohol consumption’ if implemented. A top tip for government is to make alcohol ‘less affordable by introducing a minimum price per unit’. There was much talk of growing tides of unassailable evidence. Dr No began to fear he was now King Canute, alone on the beach, his once half full glass now half empty. Until, that is, he heard an interview on the Today programme. Suddenly the glass was half full again.

Flogging toothpaste may be a dull business, but for once eyes must surely have shone brighter than teeth in the marketing department at Colgate this week. A gift of a study, published in the BMJ last Thursday, linked poor toothbrushing to heart disease. The media predictably flipped the message, with headlines certain to fix a smile on even the most jaded of Colgate lips. Auntie exhorted us to ‘Brush teeth to halt heart disease’, while the Daily Mail directed ‘Clean your teeth twice a day to keep a heart attack at bay’. The ping was at last back in the Colgate ring of confidence, for who needs advertising, when sparkling headlines (351 of them, according to google) say it all?

The research is not without interest. It kicks off with what we might call intuition bias, by echoing the old saw about an apple a day. And what could be more likely than scabby teeth means dodgy tickers, as plaque ridden teeth mirror plaque filled arteries (Dr No kids you not – one Mail commenter equates dental plaque with arterial plaque – and advises using floss to remove it!)? But what about the science?

The Hospital Manager’s Association

Top Secret – Eyes Only

The Hospital Manager’s Guide to Massaging HSMRs

Members will be aggrieved to hear that the Doctor Foster Intelligence Unit and its lottery hospital standardised mortality ratios (HSMRs) are here to stay, despite several recent papers showing the methodology to be unsound.

Members will appreciate that they supply the raw data used by Dr Foster, thus providing opportunities to ‘cook’ the figures before they are passed to Dr Foster. The Association does not condone directly tampering with the data; however, faced with the intractable use of flawed statistics, the Association does believe members are entitled to ‘game’ the system to their advantage.

There has been much ado about hospital death rates lately, much of it focused on the Mid Staffs hospitals, where consistently high apparent death rates were repeatedly brushed aside and ignored. The issue at stake was the validity - or not - of certain statistics produced by Sir Jar and his operatives at HI5, the Dr Foster Intelligence Unit, and one statistic in particular, the HSMR.

The HSMR, or Hospital Standardised Mortality Ratio to give it its full name, is said by Sir Jar to offer a useful marker of a hospital’s performance, by providing a single figure that summarises how many patients leave the hospital feet-first. High value HSMRs suggest more stiffs than expected, low HSMRs indicate less stiffs than expected, compared to national figures. Unfortunately for Sir Jar, the method – quite apart from a myriad of other factors that might compromise validity - he uses to determine HSMRs suffers from a flaw that severely restricts its application. While an isolated HMSR can be compared to the ‘big picture’ – in other words, the standard population to which it is being compared - comparisons between hospitals, or even the same hospital over time, are prone to errors, which can render the results at best meaningless, at worst misleading.

Dr No is hopeless with numbers. Just being in the presence of statisticians causes a pressure of incomprehension to build up in his head. When they start to talk numbers, it is as if they are speaking in tongues; and when their chalk squeaks on the blackboard, all he sees is so many hieroglyphics.

But numbers are part of the fabric of medicine, and their understanding is necessary to the practice of medicine; and so Dr No has over the years developed a habit of translating the hieroglyphics into words, and the formulae into verbal instructions. Σx becomes the sum total of all the values of x; and μ = Σx/n becomes find the average value of x by adding them together, and dividing by the number in the sample. The dark impenetrable pool of numeracy is side-stepped on the well-worn plank of words.

One of the most bizarre facts about modern medicine is that most of the time, for most people, most drugs don’t work. Naturally, this is something that Big Pharma is keen to keep hidden. Even most doctors are only dimly aware that most of the drugs they peddle might not always be what they are cracked up to be. At a time when drug companies and doctors are pushing ever more pills onto ever more patients, we should perhaps be a little more savvy about the pharmaceutical pact we enter into when we agree to pop pills.

For hundreds of years, doctors had few effective drugs at their disposal. Those that they did have were either herbal toxins used in small doses - opium, digitalis, quinine and the like, which most certainly did and do work - or so-called “tonics” – dubious placebos that nonetheless pleased the doctor and his patient.

Sir Liar ‘Tombstone’ Swansong, ex-CMO-elect, has let it be known that he intends to use his retirement to persuade government to impose a binding minimum price for alcohol, in the hope of curbing alcohol related harm. A figure of 50p per unit sold has been suggested – which would raise the minimum price for a bottle of 12% ABV wine to £4.50, up some 50% on today’s minimum prices.

What two things do sex and statistics have in common – apart, that is, from both starting with the letter S? The answer, of course, is firstly that in both, bigger is usually butt (sic) not always better, and secondly that both can be massaged to make things, err, stand out more.

We are drowning in number soup again.

The UK medical blogosphere is getting worked up about some numbers released last week by the Patients Association. The consensus seems to be that the numbers are a classic example of foul play by statistics. But perhaps they are not.