Statistics and the law: the prosecutor’s fallacy
Conclusions.
Although this argument uses an artificial example that is simpler than most real cases, it illustrates some important principles.
(1) The likelihood ratio is not a good way to evaluate evidence, unless there is good reason to believe that there is a 50:50 chance that the suspect is guilty before any evidence is presented.
(2) In order to calculate what we need, Prob(guilty | evidence), you need to give numerical values of how common the possession of characteristic x (the evidence) is the whole population of possible suspects (a reasonable value might be estimated in the case of DNA evidence), We ...
Source: DC's goodscience - March 22, 2016 Category: Science Authors: David Colquhoun Tags: Law statistics Clive Stafford Smith false conviction false discovery rate false positives lawyers Michael Mansfield Philip Dawid Squier Waney Squier Source Type: blogs
Placebo effects are weak: regression to the mean is the main reason ineffective treatments appear to work
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“Statistical regression to the mean predicts that patients selected for abnormalcy will, on the average, tend to improve. We argue that most improvements attributed to the placebo effect are actually instances of statistical regression.”
“Thus, we urge caution in interpreting patient improvements as causal effects of our actions and should avoid the conceit of assuming that our personal presence has strong healing powers.”
McDonald et al., (1983)
In 1955, Henry Beecher published "The Powerful Placebo". I was in my second undergraduate year when it appeared. An...
Source: DC's goodscience - December 11, 2015 Category: Science Authors: David Colquhoun Tags: acupuncture CAM placebo publishing quackademia random randomisation randomization RCT regression to the mean reproducibility statistics alternative medicine chiropractic osteopathy physiotherapy placebo effect Source Type: blogs
Placebo effects are weak: regression to the mean is the main reason ineffective treatments appear to work
“Statistical regression to the mean predicts that patients selected for abnormalcy will, on the average, tend to improve. We argue that most improvements attributed to the placebo effect are actually instances of statistical regression.”
“Thus, we urge caution in interpreting patient improvements as causal effects of our actions and should avoid the conceit of assuming that our personal presence has strong healing powers.”
McDonald et al., (1983)
In 1955, Henry Beecher published "The Powerful Placebo". I was in my second undergraduate year when it appeared. And for many decades afte...
Source: DC's goodscience - December 11, 2015 Category: Science Authors: David Colquhoun Tags: acupuncture CAM placebo publishing quackademia random randomisation randomization RCT regression to the mean reproducibility statistics alternative medicine chiropractic osteopathy physiotherapy placebo effect Source Type: blogs
How long until the next bomb? Why there ’ s no reason to think that nuclear deterrence works
Every day one sees politicians on TV assuring us that nuclear deterrence works because there no nuclear weapon has been exploded in anger since 1945. They clearly have no understanding of statistics.
With a few plausible assumptions, we can easily calculate that the time until the next bomb explodes could be as little as 20 years.
Be scared, very scared.
The first assumption is that bombs go off at random intervals. Since we have had only one so far (counting Hiroshima and Nagasaki as a single event), this can’t be verified. But given the large number of small influences that control when a bomb explodes (whether ...
Source: DC's goodscience - October 24, 2015 Category: Science Authors: David Colquhoun Tags: Politicians politics bomb deterrant exponential distribution Markov nuclear statistics Trident Source Type: blogs
How long until the next bomb? Why there ’ s no reason to think that nuclear deterrence works
Every day one sees politicians on TV assuring us that nuclear deterrence works because there no nuclear weapon has been exploded in anger since 1945. They clearly have no understanding of statistics.
With a few plausible assumptions, we can easily calculate that the time until the next bomb explodes could be as little as 20 years.
Be scared, very scared.
The first assumption is that bombs go off at random intervals. Since we have had only one so far (counting Hiroshima and Nagasaki as a single event), this can’t be verified. But given the large number of small influences that control when a bomb explodes (whether...
Source: DC's goodscience - October 24, 2015 Category: Science Authors: David Colquhoun Tags: Politicians politics bomb deterrant exponential distribution Markov nuclear statistics Trident Source Type: blogs
How long until the next bomb? Why there’s no reason to think that nuclear deterrence works
Every day one sees politicians on TV assuring us that nuclear deterrence works because there no nuclear weapon has been exploded in anger since 1945. They clearly have no understanding of statistics.
With a few plausible assumptions, we can easily calculate that the time until the next bomb explodes could be as little as 20 years.
Be scared, very scared.
The first assumption is that bombs go off at random intervals. Since we have had only one so far (counting Hiroshima and Nagasaki as a single event), this can’t be verified. But given the large number of small influences that control when a bomb explodes (whether...
Source: DC's goodscience - October 24, 2015 Category: Science Authors: David Colquhoun Tags: Politicians politics bomb deterrant exponential distribution Markov nuclear statistics Trident Source Type: blogs
How long until the next bomb? Why nuclear deterrence doesn’t work
Every day one sees politicians on TV assuring us that nuclear deterrence works because there no nuclear weapon has been exploded in anger since 1945. They clearly have no understanding of statistics.
With a few plausible assumptions, we can easily calculate that the time until the next bomb explodes could be as little as 20 years.
Be scared, very scared.
The first assumption is that bombs go off at random intervals. Since we have had only one so far (counting Hiroshima and Nagasaki as a single event), this can’t be verified. But given the large number of small influences that control when a bomb explodes (whether...
Source: DC's goodscience - October 24, 2015 Category: Science Authors: David Colquhoun Tags: Politicians politics bomb deterrant exponential distribution Markov nuclear statistics Trident Source Type: blogs
The perils of P values, in Chalkdust magazine
Chalkdust is a magazine published by students of maths from UCL Mathematics department. Judging by its first issue, it’s an excellent vehicle for popularisation of maths. I have a piece in the second issue
You can view the whole second issue on line, or download a pdf of the whole issue. Or a pdf of my bit only: On the Perils of P values.
The piece started out as another exposition of the interpretation of P values, but the whole of the first part turned into an explanation of the principles of randomisation tests. It beats me why anybody still does a Student’s t test. The idea of randomisation tests is very ...
Source: DC's goodscience - October 6, 2015 Category: Science Authors: David Colquhoun Tags: statistics altmetrics bibliometrics false discovery rate false positives randomisation randomization Source Type: blogs
The perils of P values, in Chalkdust magazine
Chalkdust is a magazine published by students of maths from UCL Mathematics department. Judging by its first issue, it’s an excellent vehicle for popularisation of maths. I have a piece in the second issue
You can view the whole second issue on line, or download a pdf of the whole issue. Or a pdf of my bit only: On the Perils of P values.
The piece started out as another exposition of the interpretation of P values, but the whole of the first part turned into an explanation of the principals of randomisation tests. It beats me why anybody still does a Student’s t test. The idea of randomisation tests is very...
Source: DC's goodscience - October 6, 2015 Category: Science Authors: David Colquhoun Tags: statistics altmetrics bibliometrics false discovery rate false positives randomisation randomization Source Type: blogs
Stefan Grimm (1963 – 2014). A memorial to a victim of managerialism
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Today, 25 September, is the first anniversary of the needless death of Stefan Grimm. This post is intended as a memorial.
He should be remembered, in the hope that some good can come from his death.
On 1 December 2014, I published the last email from Stefan Grimm, under the title “Publish and perish at Imperial College London: the death of Stefan Grimm“. Since then it’s been viewed 196,000 times. The day after it was posted, the server failed under the load.
Since than, I posted two follow-up pieces. On December 23, 2014 “Some experiences of life at Imperial Colleg...
Source: DC's goodscience - September 24, 2015 Category: Science Authors: David Colquhoun Tags: Academia business corporate corruption Imperial metrics Alice Gast bibliometrics Gavin Screaton Imperial College managerialism Martin Wilkins Stefan Grimm Universities Source Type: blogs
Stefan Grimm (1963 – 2014). A memorial to a victim of managerialism
Jump to follow-up
Today, 25 September, is the first anniversary of the needless death of Stefan Grimm. This post is intended as a memorial.
He should be remembered, in the hope that some good can come from his death.
On 1 December 2014, I published the last email from Stefan Grimm, under the title “Publish and perish at Imperial College London: the death of Stefan Grimm“. Since then it’s been viewed 196,000 times. The day after it was posted, the server failed under the load.
Since than, I posted two follow-up pieces. On December 23, 2014 “Some experiences of life at Imperial Colleg...
Source: DC's goodscience - September 24, 2015 Category: Science Authors: David Colquhoun Tags: Academia business corporate corruption Imperial metrics Alice Gast bibliometrics Gavin Screaton Imperial College managerialism Martin Wilkins Stefan Grimm Universities Source Type: blogs
Stefan Grimm (1963 – 2014). A memorial to a victim of managerialism
Jump to follow-up
Today, 25 September, is the first anniversary of the needless death of Stefan Grimm. This post is intended as a memorial.
He should be remembered, in the hope that some good can come from his death.
On 1 December 2014, I published the last email from Stefan Grimm, under the title “Publish and perish at Imperial College London: the death of Stefan Grimm“. Since then it’s been viewed 196,000 times. The day after it was posted, the server failed under the load.
Since than, I posted two follow-up pieces. On December 23, 2014 “Some experiences of life at Imperial Colleg...
Source: DC's goodscience - September 24, 2015 Category: Science Authors: David Colquhoun Tags: Academia business corporate corruption Imperial metrics Alice Gast bibliometrics Gavin Screaton Imperial College managerialism Martin Wilkins Stefan Grimm Universities Source Type: blogs
Stefan Grimmm (1963 – 2014). A memorial to a victim of managerialism
Jump to follow-up
Today, 25 September, is the first anniversary of the needless death of Stefan Grimm. This post is intended as a memorial.
He should be remembered, in the hope that some good can come from his death.
On 1 December 2014, I published the last email from Stefan Grimm, under the title “Publish and perish at Imperial College London: the death of Stefan Grimm“. Since then it’s been viewed 196,000 times. The day after it was posted, the server failed under the load.
Since than, I posted two follow-up pieces. On December 23, 2014 “Some experiences of life at Imperial Colleg...
Source: DC's goodscience - September 24, 2015 Category: Science Authors: David Colquhoun Tags: Academia business corporate corruption Imperial metrics Alice Gast bibliometrics Gavin Screaton Imperial College managerialism Martin Wilkins Stefan Grimm Universities Source Type: blogs
There are powerful currents whipping up the metric tide. The HEFCE metrics report
This is very quick synopsis of the 500 pages of a report on the use of metrics in the assessment of research. It’s by far the most thorough bit of work I’ve seen on the topic. It was written by a group, chaired by James Wilsdon, to investigate the possible role of metrics in the assessment of research.
The report starts with a bang. The foreword says
"Too often, poorly designed evaluation criteria are “dominating minds, distorting behaviour and determining careers.”1 At their worst, metrics can contribute to what Rowan Williams, the former Archbishop of Canterbury, calls a “new b...
Source: DC's goodscience - July 9, 2015 Category: Science Authors: David Colquhoun Tags: Academia HEFCE altmetrics bibliometrics Universities vice-chancellors Source Type: blogs
Are women still at a disadvantage in science?
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There can be no doubt that the situation for women has improved hugely since I started at UCL, 50 years ago. At that time women were not allowed in the senior common room. It’s improved even more since the 1930s (read about the attitude of the great statistician, Ronald Fisher, to Florence Nightinglale David).
Recently Williams & Ceci published data that suggest that young women no longer face barriers in job selection in the USA (though it will take 20 years before that feeds through to professor level). But no sooner than one was feeling optimistic, along comes Tim Hunt who caused a media sto...
Source: DC's goodscience - June 15, 2015 Category: Science Authors: David Colquhoun Tags: diversity racism Research Councils Research Funding Research managers Royal fellows Royal Society UCL University College London women Academia HR Human resources performance management Peter Lawrence science Stefan Grimm Source Type: blogs
