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In this case, because pancreatic cancer is relatively rare, the impressive-sounding 50% reduction doesn't amount to very much. According to the American Cancer Society, a 60-year-old man has a 0.41% (1 in 241) chance of developing pancreatic cancer during the next ten years. (Risk varies greatly with age and is much lower at younger ages.) So cutting that risk in half might bring it down to about 0.2% (1 in 480). It's a 50% drop, sure, but the risk was already very small to begin with. In this case, it's more helpful to news and health care consumers to describe it as a 0.2 percentage point reduction. And then there are the harms of regular aspirin use; the Yale news release that the tweet links to doesn't mention any. But taking aspirin regularly isn't a harmless intervention - far from it. It's well known that taking aspirin every day can cause serious bleeding in the gastrointestinal system and, less frequently, in the brain. That's why guidelines for aspirin use in cardiovascular disease prevention don't recommend it for people at low risk of a heart attack. The potential benefits may be outweighed by the risks of a serious bleed.

Many public conversations we have about science-related issues involve communicating risks: describing them, comparing them and trying to inspire action to avoid or mitigate them. Just think about the ongoing stream of news and commentary on health, alternative energy, food security and climate change. Good risk communication points out where we are doing hazardous things. It helps us better navigate crises. It also allows us to pre-empt and avoid danger and destruction. But poor risk communication does the opposite. It creates confusion, helplessness and, worst of all, pushes us to actively work against each other even when it's against our best interests to do so. So what's happening when risk communications go wrong?

You may have heard the advice for pregnant women to avoid eating soft cheeses. This is because soft cheeses can sometimes carry the Listeria monocytogenes bacteria, which can cause a mild infection. In some cases, the infection can be serious, even fatal, for the unborn child. However, the infection is very rare, affecting only around 65 people out of 23.5 million in Australia in 2014. That's 0.0003% of the population. Of these, only around 10% are pregnant women. Of these, only 20% of infections prove fatal to the foetus. We're getting down to some very small numbers here. If we talked about every risk factor in our lives the way health authorities talk about soft cheeses, we'd likely don a helmet and kneepads every morning after we get out of bed. And we'd certainly never drive a car. The upshot of this example is to emphasise that our intuitions about risk are often out of step with the actualities. So journalists need to take great care when reporting risk so as not to exacerbate our intuitive deficits as a species.

Interesting discussion of how we perceive risk, and the risks of everyday activities! So let's answer the first question: how likely is a fatal shark attack for an Australian? To get a crude estimate of this, averaged across the whole population, you would divide the number of people who have died due to a shark attack each year (on average three to four each year based on recent data) by the population of Australia (approximately 24 million). This yields a risk of approximately one in eight million per year, which is thankfully very low. Does this assuage your fear? If not, the reason is probably that the imagery of a shark attack is so terrifying. Any unusual and dramatic event has a huge impact on our psyche and this distorts our perception. Also, it's not that easy for us to interpret what a risk expressed as a relative frequency truly means.

Excellent discussion of absolute and relative risk in the context of alcohol safety. "But claiming there is no 'safe' level does not seem an argument for abstention. There is no safe level of driving, but government do not recommend that people avoid driving."

how could two groups of 'experts' come up with such different conclusions, given they broadly agree of the evidence? David Aaronovitch in the Times identified the critical underlying issue behind the ensuing conflict: whether we take an individual- or a population-based approach. Essentially, the authors point out that any absolute risks are small from an individual perspective, and may generally be cancelled out by the enjoyment of eating, and the bother of changing habits. But these small benefits can be important from a public-health, population-wide perspective, since a lot of people making a small change, that only reduces their risk by a personally-negligible amount, can add up to thousands fewer cases of disease. That's what has generated the disagreement. It can be perfectly reasonable for guidance to be given by authorities, and it can also be perfectly reasonable for individuals to ignore it. Both can be 'right'.

How excited would you be about a medication that lowered your risk of cardiovascular death, heart attack or stroke by 1.5%? Excited enough to spend a few thousand dollars a year on the drug? I expect not. What if, instead, the drug reduced those same terrible outcomes by 20%? That's probably enough benefit to interest some in the drug. Well, those statistics come from the same clinical trial, evaluating the same drug. In fact, they present the exact same results, but they simply do it in different ways.

Today's Examine dives into the maths. We'll look at the best estimates on catching and being injured by COVID-19, the chances of being harmed by the AstraZeneca vaccine, and the other broader risks and benefits. Hopefully, at the end of this, you are armed to make a better decision.

almost all the stories I looked at emphasized that "1 in 10 pregnant women" with Zika gave birth to babies with birth defects.But how many actual women does the "1 in 10" figure represent? How many actual babies with birth defects?You have to wade far down into all of these stories to find the numbers, whereas NPR puts them right in its headline:51 Babies Born With Zika-Related Birth Defects In The U.S. Last YearThe fact that 1 in 10 women with Zika have babies with birth defects is accurate but not nearly as informative as it could be.And when communicating to a general audience, it's misleading to the point of scaremongering to make the "1 in 10" headline the take-home message from the study.

During the 2016 EU referendum campaign, both sides used statistics pretty freely to back their arguments. Understandably, UK broadcasters felt compelled to balance competing perspectives, giving audiences the opportunity to hear the relative merits of leaving or remaining in the EU. In doing so, however, the truth of these statistical claims was not always properly tested. This might help explain some of the public's misconceptions about EU membership. So, for example, although independent sources repeatedly challenged the Leave campaign's claim that the UK government spent £350m per week on EU membership, an IPSOS MORI survey found that almost half of respondents believed this was true just days before the election. Of the 6,916 news items examined in our research, more than 20% featured a statistic. Most of these statistical references were fairly vague, with little or limited context or explanation. Overall, only a third provided some context or made use of comparative data. Statistics featured mostly in stories about business, the economy, politics and health. So, for example, three-quarters of all economics items featured at least one statistic, compared to almost half of news about business. But there were some areas - where statistics might play a useful role in communicating trends or levels of risk - that statistics were rarely used.