Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!floyd!harpo!seismo!hao!hplabs!sri-unix!Barker.PA@PARC-MAXC.ARPA From: Barker.PA@PARC-MAXC.ARPA Newsgroups: net.physics Subject: Re:Correction to my Helmut Schmidt article Message-ID: <16483@sri-arpa.UUCP> Date: Tue, 7-Feb-84 11:47:00 EST Article-I.D.: sri-arpa.16483 Posted: Tue Feb 7 11:47:00 1984 Date-Received: Fri, 10-Feb-84 03:16:43 EST Lines: 60 Lew, I have followed this subject with keen interest, I have even obtained a gieger counter to fool around with. There are a couple of confusiong points about your last message. First you mention that someone has stated that the data presented in the graph is movement to the right above average. However, stasticly average is zero. If however you mean the average number of steps away from center in either direction that number is given by the square root of the number of total steps and is therefore about 77. Even so the data that I saw on the nova program was compared to a curve of random data centered around zero, as if the were implying that the deviation was away from a random walk that resulted in no net average displacement. I agree with your earlier computer simulation and have generated the same datsa myself. I have also evaluated the probabilities for a random walk according to the following formula P(X) = (1/2)**N*N! / (X!*((NX)/2)!) where N is total number os steps and P(X) is the prob. of landing on the Xth step. which gives the following results, # P(X) total P(all steps below X) step= +/- 0 .010300216203 .010300216203 step= +/- 1 .000000000000 .010300216203 step= +/- 2 .020593567883 .030893784085 step= +/- 3 .000000000000 .030893784085 step= +/- 4 .020572988035 .051466772120 step= +/- 5 .000000000000 .051466772120 step= +/- 6 .020538733975 .072005506095 step= +/- 7 .000000000000 .072005506095 step= +/- 8 .020490874076 .092496380171 step= +/- 9 .000000000000 .092496380171 step= +/- 60 .015261862398 .569012209115 step= +/- 61 .000000000000 .569012209115 step= +/- 120 .006205475647 .881743699915 step= +/- 121 .000000000000 .881743699915 step= +/- 240 .000169454944 .998139688874 Points to be made are that there is almost a 12% chance that the data will come out with a displacement above 120. Not hard to reproduce in a lab. The chance that it will be beyond 240 is .2 % not 1/10000. 1/10000 is closer to the probability that the displacement is on step # 240 ONLY