How to explain screening test outcomes

Consider the following problem: “The serum test screens pregnant women for babies with Down's syndrome. The test is a very good one, but not perfect. Roughly 1% of babies have Down's syndrome. If the baby has Down's syndrome, there is a 90% chance that the result will be positive. If the baby is unaffected, there is still a 1% chance that the result will be positive. A pregnant woman has been tested and the result is positive. What is the chance that her baby actually has Down's syndrome?”

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What is the most popular birthday in England and Wales?

The UK Office for National Statistics (ONS) recently published an analysis of live births from 1995 to 2014 and concluded that, in England and Wales, 26 September was “the most popular day to be born over the last two decades”. The ONS points out that September, more generally, is the period in the year with a seasonal peak in the number of births. It is not difficult to establish the cause of this phenomenon: a seasonal peak of conceptions around Christmas time.

Remembering Hans Rosling

Credit: Overseas Development Institute
Professor Hans Rosling, a statistician and public educator who was committed to sharing the joy - and importance - of statistics, died yesterday. In a statement posted on the Gapminder website, his son and daughter-in-law, Ola Rosling and Anna Rosling Rönnlund, explained that Prof. Rosling had been diagnosed with pancreatic cancer a year ago and that he had passed away early Tuesday morning, surrounded by his family in Uppsala, Sweden.

Groundhog Day: the truth about these furry forecasters

The groundhog has evolved into a winning combination of cute and ungainly. This burrowing squirrel may resemble a furry cube with a leg at each corner, but do not be deceived by its bumbling, hapless charms: this is a Nostradamus of the animal world. In North American folklore, the groundhog can apparently be used to foresee the future, as many a town in the US and Canada will have vouched on February 2 as they celebrated Groundhog Day.