Lies, Damn Lies and Doctors who are bad a... - Healthy Evidence

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Lies, Damn Lies and Doctors who are bad at maths

JossS profile image
11 Replies

A wonderful article about the misunderstanding of statistics not just by patients but by huge numbers of practicing doctors.

bbc.co.uk/news/magazine-281...

I was particularly interested in the explanation of Survival rates as opposed to Mortality rates which shows that, despite common belief to the contrary, about the same percentage of men die of Prostate Cancer in the UK as in the US.

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JossS profile image
JossS
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11 Replies
teessidesitp profile image
teessidesitp

Statistics must be the most misunderstood branch of mathematics that is used daily by most people but I think that may be because it has been subject to the worst of political, financial and every-day abuse by the media.

If any article gives simple percentages to back up a point of view without going into details about how they were arrived at then you can dismiss them as unproven or even made up. I have used this as a guide to myself over the last decade or so and it works fine. The problem is that it takes a long time to dig into the trail of information leading to a scientific or mathematical paper and sometimes it costs a fortune to get access to that paper. Nothing is easy even in the age of the Internet.

Emily_Jesper profile image
Emily_JesperPartnerSense About Science

We've a guide to making sense of statistics. It provides the questions to ask ("If a statistic is the answer, what was the question?") and identifies the pitfalls to avoid to help us get behind news stories that use statistics: senseaboutscience.org/resou...

Bioburden profile image
Bioburden

Misuse of statistics is only half of the problem. Framing the research question to deliver desirable results is a source of distortion; selecting a sample population that excludes certain groups, having short follow-up times, 'cleaning the data' of outliers............

Doctors don't have time to examine actual trial data, even if it is all disclosed, they rarely have time to read beyond the manufacturer's marketing piece that positions good data to the fore.

DrCommsense profile image
DrCommsense

This 'wonderful' article is entertaining, provocative and 'good copy' but misleading. If someone purports to have the appropriate data to find the prior probability (1%), the sensitivity (90%) and the specificity (91% and thus false alarm rate of 9%) of a test result, then they should simply count the number of patients with the diagnosis in those with the test result in that population (the 'predictiveness'). There is no need to apply Bayes theorem to 'calculate' that it is 10%. The trouble is that the sensitivity and specificity can look impressive (like relative risk) and as the prevalence depends on the population of patients you choose to measure the prevalence, it is easy to use Bayes theorem to calculate any level of 'predictiveness' to surprise or impress your audience.

StuartJones profile image
StuartJones in reply to DrCommsense

@Drcommonsense I would say most patients find the concept of probability easier to understand than "predictiveness" when having results explained? Nothing misleading about saying "your test result means there is a 10% chance you have the disease". I thought it was a nice article!

Statto profile image
Statto

I wrote an article in the Guardian a few years ago, on a similar theme. The Government were trying to justify their healthcare reforms on some very dubious statistical claims.

guardian.co.uk/commentisfre...

Vitruvia profile image
Vitruvia

Good example of a spelling mistake spreading like a virus. If you search for 'prostrate cancer' there are currently 88 links. If you look up 'prostate cancer' the results list completely different articles. People could miss valuable information here. Depressing.

JossS profile image
JossS

Or in my case, I assume the autocorrect on my tablet doing its thing, as normal.

Thankfully, if you search on Google, it corrects you anyway.

However, I just noticed that my post was edited by someone called Joel - who is that? Maybe it wasn't my autocorrect after all.

Emily_Jesper profile image
Emily_JesperPartnerSense About Science in reply to JossS

Hi Joss

The BBC link stopped working so the HealthUnlocked guys fixed it. Thanks! Emily

JossS profile image
JossS in reply to Emily_Jesper

Thanks Emily - Can you bung them a message asking them to put a note at the bottom of the post, like "Edit: fixed broken link?"

Its always useful for people to know why something was changed. :)

Emily_Jesper profile image
Emily_JesperPartnerSense About Science in reply to JossS

Will do, thanks Joss.

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