Probability and astonishment

     A small poem by Lia Purpura in the January 29, 2015 issue of The New Yorker delights even as it highlights the errors that many of us make in supposing that coincidences -- such as meeting some home town friend in a distant vacation spot -- are rare rather than probable.  

       Probability     by Lia Purpura

       Most coincidences are not
       miraculous, but way more
       common than we think--
       it's the shiver
       of noticing being
       central in a sequence 

Probability and Coincidence

     On page 26 of my copy of the latest New Yorker is a poem by Lia Purpura entitled "Probability."  In her brief poem Purpura renders with poetic power the astonishment each of us feels when meeting a long-ago classmate at an out-of-town super market or some other unexpected event.  Take time to follow the link and read this poem.
     Recently several friends have shared with me their amazement at unexpected coincidences and I have been tempted to illustrate -- perhaps with the birthday paradox --  how likely to happen unexpected events may be.

  With more than 23 persons in a room the chances are more than 50-50

 that two of them will share a birthday (same day, maybe different years).

Many websites offer explanation of this "birthday paradox" -- here is one.