# How Certain Are You About Uncertainty? A Knighted British Statistician Knows Your Limits

Professor Sir David Spiegelhalter at play

Ask a statistician to explain a coincidence and you will hear something like:

In large populations any strange thing can happen.
You remember only the personally charged coincidences and don’t notice the many other coincidences happening around you.

Professor Sir David Spiegelhalter is no exception. He loves coincidences. He loves studying coincidences. His website Understanding Uncertainty has collected more than 4000 coincidence stories for him to mull over. He marvels at their frequency in people’s lives and how they understand and use them. He rarely notices them himself. He wants to convince you that statistics offer the best explanation.

A Brief Bio
Sir Spiegelhalter aims to improve the way statistical evidence is used by health professionals and patients. He advises organizations and government agencies on risk communication and is a regular media commentator on statistical issues, with a particular focus on communicating uncertainty.

He is the author of Sex by Numbers, and The Art of Statistics. He was elected Fellow of the Royal Society in 2005, knighted in 2014 for services to medical statistics, and was President of the Royal Statistical Society for 2017-2018.
He considers himself a policeman of science whose job it is to make sure that data suggesting a pattern really show demonstrate a pattern. Apophenia, seeing patterns that aren’t there, is one of his favorite words. Valuable contributions!

He helps medical patients understand the probabilities involved with the prognosis of their diseases. Very important because physicians and nurses are rarely trained in probability.

A Cluster Analysis

The Quid group analyzed the content of the stories on his website. They found:

Sharing a birthday with someone (11%)
Probability easily explains sharing a birthday—you have a 1/365 chance of that happening. It has to happen.

Connections involving books, TV, radio, or the news (10%)
Connections involving books and media was difficult for Sir Spiegelhalter to explain. Media coincidences commonly occur by respondents to the Weird Coincidence Survey.

Vacation-related coincidences (6.1%)
Running into someone you know on vacation can be explained by both of your being in a similar socio-economic group that travels to similar vacation spots.

Meeting people in transit—while walking around, in airports, or on public transportation (6%)
They may be people you know, and people who become meaningful to you.

Coincidences related to marriage or in-laws (5.3%)
Coincidences related to family members, covers a wide variety of possibilities including Simulpathity (feeling the pain of a loved one at a distance)

Professor Spiegelhalter would like you to believe that statistics provide the best explanation for all of these coincidences. Would he consider the conventionally accepted psychodynamic explanation for some of them?

He reported his own remarkable coincidence:
“I was on a radio show working with several people. I was choosing a date since one of my favorite coincidence stories was about matching birthdays, and I had forgotten the date. I paused for a moment and picked this date. It matched the birthdays of 2 of the people with whom I was working. The probability that they had the same birthday was 1 in 365, and the probability that my ‘random’ choice matched it is 1 in 365, making it about 1/ 135,000 ( 1/365×1/365 = 133,225).

To listen to his lively exchange with me, click here

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