 
you chose ... you are the rain drops are clumped towards the middle In fact, each rain drop fell independently of the rest, so there is a string random element, but they also had a tendency to fall towards the centre of the pavement. Compare this with the pattern for day 1. You will find that they have exactly the same number of empty tiles, overfull squares etc. In fact, if you plot the distribution of the number of tiles with a given number of rain drops in, you will find the two distributions are identical. Did you think day 1 was random too? They are similar in many ways, but day 2 has a systematic unevenness  all the overfull tiles are in the centre.
back to: the story  day 1  day 2  day 3  statistics tutorial 

http://www.meandeviation.com/tutorials/stats/story/l 
Alan Dix 5/8/98 