Let's get back to earthquakes
Posted by Roger Hunter on June 18, 2006 at 07:09:15:

Hi all;

Here are two series of events happening over time.
What would you conclude from them?


F............N.............F............N.............
...Q.......Q........Q........Q.......Q..............Q.
F............N.............F............N.............
.Q...........Q...........Q..........Q.........Q.......
F............N.............F............N.............
...Q........Q........Q.........Q...........Q........Q.
F............N.............F............N.............
....Q.......Q......Q......Q......Q........Q...........

Consider each dot to be a day and the lines to be continuous.
We have two lines, each 224 days long, broken into 56 day
segments. A seismogram looks like this except it's only
one line.

Now the top line has F and N in it, 16 in all. The next line
has Q in it, 23 of them. Would you say that there is a causal
relationship between the F or N and the Q? Notice that there
are a number of close calls. One case is on the same day, 5
cases are within +-1 day (3 day window) and 9 cases are within
+-2 days (5 day window). 9 cases, that must mean something.
Right? It's 39% of the Qs.

Wrong. It's just chance. A 5 day window has (5*16)/224 = 35.7%
chance of success and the 1 extra hit is not significant.

This is the trap that Shan, Berkland and many others have fallen
into. They count the hits and forget the misses.

Roger

Follow Ups:
     ● Re: Let's get back to earthquakes - Barbara  08:03:33 - 6/18/2006  (38444)  (1)
        ● Re: Let's get back to earthquakes - Roger Hunter  09:12:43 - 6/18/2006  (38446)  (3)
           ● Re: Let's get back to earthquakes - marc / berkeley  13:59:20 - 6/18/2006  (38466)  (1)
              ● Re: Let's get back to earthquakes - Roger Hunter  14:21:55 - 6/18/2006  (38470)  (1)
                 ● Re: Let's get back to earthquakes - marc / berkeley  14:34:32 - 6/18/2006  (38472)  (1)
                    ● Re: Let's get back to earthquakes - Roger Hunter  14:51:27 - 6/18/2006  (38473)  (1)
                       ● Re: Let's get back to earthquakes - marc / berkeley  11:36:33 - 6/19/2006  (38520)  (1)
                          ● Re: Let's get back to earthquakes - Roger Hunter  12:31:50 - 6/19/2006  (38524)  (0)
           ● Re: Let's get back to earthquakes - Barbara  10:41:09 - 6/18/2006  (38452)  (1)
              ● Re: Let's get back to earthquakes - Roger Hunter  14:24:14 - 6/18/2006  (38471)  (0)
           ● Re: Let's get back to earthquakes - Russell  10:20:24 - 6/18/2006  (38450)  (1)
              ● Re: Let's get back to earthquakes - Roger Hunter  10:39:44 - 6/18/2006  (38451)  (1)
                 ● Re: Let's get back to earthquakes - Russell  11:04:55 - 6/18/2006  (38455)  (0)