What do you need to know the truth about?

b = a ab = a 2 ab – b 2 = a 2 – b 2 b(a – b) = (a + b)(a – b) b = a + b b = 2b 1 = 2

‘I reflect the fundamental truths of the universe.’

What do you need to know the truth about?

MMR

Consequences ● The proportion of people vaccinated against measles has dropped to 61% in some areas ● In 2008, measles was declared 'endemic' in the UK, meaning people cannot rely upon heard immunity ● There were 8482 measles cases in 2013 in the UK

The Lawsuits ● Nearly 5000 cases of parents claiming compensation from vaccination companies in the USA ● Despite almost all of them being unsuccessful, they continue to be brought. ● In the UK, the cases have been consolidated into a group which has received £15 in public legal aid funding

News Reports in 2002 ● 1,257 articles were published about the link between MMR and autism. ● Almost all were written by non-experts, mostly journalists. ● 26% of doctors felt the government had 'failed to prove there was no link'

The Original Paper Twelve children were recruited by a newsletter about MMR concerns publishing a plea to study children with bowel issues. Eight of the children started to have bowel and behavioural symptoms after the MMR vaccination. These were suggested to be a new syndrome: autistic enterocolitis. The paper recommended further study into the possible link, but said it did not prove an association.

Statisticians! ● 8 out of 12 – is that significant? ● What do we mean by significant?

The key question: ● Is the result unlikely enough for us to be suspicious? ● Or should we stick with our null hypothesis?

Statisticians! ● 8 out of 12 – is that significant? ● 1% of people have autism spectrum disorder ● So we would expect 1 or 2 out of 12 to show autistic behaviour ● But it depends on the sampling! Bowel issues and autism are linked.

The Study ● Wakefield received £ to find evidence with which to sue vaccination producers ● The British Medical Journal has since investigated. They found that for all 12 children, either their diagnoses or the dates had been altered in the paper. ● This investigation received very little press coverage

Flaherty (biologist): “The most damaging medical hoax of the last 100 years” Paul Offit (pediatrician): “That paper killed children”

SIGNIFICANT...but not true!

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First Guess Good guess = luck + skilled Bad guess = unlucky + unskilled Next time, we expect 'average luck' for everyone

Second Guess Good guess = luck + skilled Next time: average luck + skilled Bad guess = unlucky + unskilled Next time: average luck + unskilled

“On many occasions I have praised flight cadets for clean execution of some aerobatic manoeuvre, and in general when they try it again, they do worse. On the other hand, I have often screamed at cadets for bad execution, and in general they do better the next time. So please don’t tell us that reinforcement works and punishment does not, because the opposite is the case.”

Regression to the Mean

When does this happen? Whenever we act on people's past performance!

Sets in school Bonuses and promotions in companies 'Performance management' Selection of students by universities/for scholarships Re-takes! Setting up speed cameras Rehabilitation of criminals Success of homeopathy Child stars Medical trials which group people by perfomance

Interventions targeting individuals classified as “high-risk” have become common-place in health care. Typically, such individuals are invited to participate in an intervention intended to reduce their level of risk, and after a period of time, a follow-up measurement is taken. However, individuals initially identified by their outlier values will likely have lower values on re-measurement in the absence of an intervention. This statistical phenomenon is known as “regression to the mean” and often leads to an inaccurate conclusion that the intervention caused the effect. Concerns about RTM are rarely raised in connection with most health care interventions, and it is uncommon to find evaluators who estimate its effect.

How can we fix it? ● We need to know about it! ● We can calculate how much change we would expect, based on regression to the mean, and see if we have more than that. ● Control groups

What do you need to know the truth about?

I had the most satisfying Eureka experience of my career while attempting to teach flight instructors that praise is more effective than punishment for promoting skill-learning. When I had finished my enthusiastic speech, one of the most seasoned instructors in the audience raised his hand and made his own short speech, which began by conceding that positive reinforcement might be good for the birds, but went on to deny that it was optimal for flight cadets. He said: