1 Norovirus, or winter vomiting disease, is back. The subject of annual warnings about how many are retching (three million last winter), reports fail only to tell us how we arrive at this number. Too many bureaucrats there may be, but still not enough to spy on every bathroom, so all we really know about are the few hundred cases confirmed in the lab. We then extrapolate to the whole population according to a formula arrived at by studying, some years ago, intestinal illness in one small town where the sample of those with confirmed cases of Norovirus was, wait for it, 1. Extrapolating from 1 is, er, heroic and so uncertain that the true number vomiting last year could have been anywhere between a modest 280,000 and a torrential 34 million.

2 About the bad times, Noël Coward was wrong, according to the Royal Geographical Society. It depends around which corner you look. A survey of Britain's happiest places found that it was mostly gleeful up north. Happiest of all was Powys; grumpiest was Edinburgh, allegedly. They know this having asked all of about 20 people in each place, making the differences - as the small print admitted - “statistically insignificant” (crude translation: rubbish). That is, the whole league table was probably determined by random variation, or chance. Not that this detained TV crews on their way to Brecknock. The survey also flatly contradicted reports by pollsters in 2006 that only three places were happier than Edinburgh. Maybe a lot happened in two years to turn Scotland's once chirpy capital into a slough of despond. Maybe, as the nation's local worthies ruminate on their rankings, we should all just laugh.

3 Hard on the heels of its knife-crime initiative, the Government - “building trust in statistics” - hailed a 17 per cent fall in serious injuries and deaths and a 27 per cent fall in hospital admissions due to knife crime. This won the distinction of being the first example of numerical knavery to be firmly smacked down by the new Statistics Authority.

And not only - as the Home Secretary sneakily implied - for being “too quick off the mark”, but also for cherry-picking data and refusing to release the rest. This raised the suspicion that the figures were erratic enough that they could be made to show just about anything, if you picked the right interval between peaks and troughs. Warnings from the National Statistician to hold fire were ignored, thus breaking three provisions of the statistical code. Brazen.

4 Another day, another crime against crime figures: apparently crimes of violence had not always been counted as such if no one was injured. Presumably a would-be axe murderer could flail through a church congregation, but this would be classed as non-violent if he failed to connect. Fear not, said the Home Office, this was simply a category error: no extra crimes were missed, just mislabelled. Ministers said it was all the fault of the police for classifying cases of “grievous bodily harm with intent” as “minor assault”, though it was also suggested that this was but another creative response to Home Office targets, in this case to reduce violent crime.

5 Figures from Scotland's health statisticians on the success rates of surgeons can't be trusted as a guide to who offers the best treatment. Says who? Say Scotland's commendably honest health statisticians. Forced to provide the data by the Scottish Information Commissioner, they did so with an astonishing caveat utilitor: “...do not provide reliable information...can act against the public interest”. The fear was that the best surgeons taking on the hardest cases or those pioneering new treatments could register the worst mortality rates, and that a difference of one or two deaths for any individual surgeon could look meaningful but simply be chance. Meanwhile, England prepares to release such figures too, not with reluctance but eagerness.

6 The rate of cervical cancer in teenagers has been rising by 6.8 per cent a year for the past 25 years - up five times overall - a conference on teenage health was told. Teen promiscuity was promptly presumed and condemned. So it was almost disappointing that 6.8 per cent turned out to equal about 0.1 to 0.2 cases a year (one extra case every five or ten years), leaving a total figure so small, and so little changed, that any conclusion about its greater social import would be fanciful. Who knows what teenagers are up to? This data did not enlighten us.

7 The British Retail Consortium declares a retail sales' crisis month after month, offering like-for-like sales, which don't count new stores, as the headline measure of its gloom. Imagine what happens to a branch of M&S when a new Sainsbury's and John Lewis open on either side of it. The M&S sales fall. See how the whole high street suffers? Like-for-like sales are a useful indicator for a single store, but dodgy for overall high street health. Official data on total retail sales may now be on its way down, and who knows how fast. But by value it has been steady almost all year and by volume has mostly been rising.

8 UK births since 2000 have risen by about 10 per cent. Down's syndrome births in the same period rose faster, at about 25 per cent despite prenatal screening. So more people are deciding to keep Down's babies. Ergo, society is “more caring”.

Big story, wishful thinking and bad statistics, which manage to ignore the one fact that most of us know about Down's: the risk increases sharply with maternal age, (1 in 1,600 births at age 25, about 1 in 100 at age 40). Many more women are having babies later; births to over 40s have increased by about 65 per cent since 2000. Put aside “caring”, we should see the birth of more Down's babies simply as a result of the changing parental age-profile. Take this into account and rates of termination turn out to be not much changed.

9 Not healthy but deadly: some vitamin supplements were found to cause a 14 per cent increase in the risk of mortality, said the man on telly, propped up on a placard bearing that number, as though at the bar of the local. Funny, but wasn't the risk of mortality quite high already? Like 100 per cent? Vitamin supplements apparently make death even more certain than certain. Only if you say at what dose (very high), for which group (the elderly), over what period or event (in a single year, for example, not a lifetime), does an increase in the risk of death mean something.

10 It's a record! Debt here, debt there, all greater than ever - and the recession scarcely begun. Well, yes, if you take cash figures, if you ignore the effect of inflation and ignore the size of the economy, as if a £10 debt meant the same to your granny in childhood as it would in 2008 to someone in their earning prime. Only then is the number of pounds of debt “a record”. Play this game with the National Debt and we find that it has hit “a record” in about 50 of the past 60 years. Real records for government deficits may be on the way.

Andrew Dilnot and Michael Blastland are the authors of The Tiger that Isn't: Seeing Through a World of Numbers, published by Profile Books

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