Prompted by an ever-growing flow of statistical questions from overseas, Stat-Ease Consultant Wayne Adams, recently circulated this Wikipedia link that provides a breakdown on countries using a decimal point versus a comma for the radix point—the separator of the integer part from the fractional side of a number.
For more background on decimal styles over time and place see this Science Editor article by Amelia Williamson. It credits Scottish mathematician John Napier* for being the first to use a period. However, it seems that he wavered later by using a comma, thus setting the stage for this being an alternative. Given the use of commas to separate thousands from millions and millions from billions and so on, numbers can be misinterpreted by several orders of magnitude very easily if you do not keep a sharp eye on the source.
So, all you math & stats boffins—watch it!
*As detailed in this 2009 blog I first learned of this fellow from seeing his bones on display at IBM’s Watson Research Center in New York.