weemba@brahms.BERKELEY.EDU (Wimpy Math Grad Student) (07/04/86)
In article <1314@psivax.UUCP> friesen@psivax.UUCP (Stanley Friesen) writes: > Take a group of about >20 people, what do you think the chances of two of them having the >same birthday are? In point of fact, it is virtually certain that >there will be at least one such pair! Uh, not exactly. Here's a list of some of the probabilities of a match: 23: 0.5073 32: 0.7533 41: 0.9032 50: 0.9704 57: 0.9901 ucbvax!brahms!weemba Wimpy Grad Student/UCB Math Dept/Berkeley CA 94720
gwyn@brl-smoke.ARPA (Doug Gwyn ) (07/05/86)
Gee, weemba, I surprised you didn't also notice that Friesen misapplied the 23-birthday principle. What he said would be equivalent, in terms of birthdays, to saying that in a room of 50 people if someone stood up and said "My birthday is the fifth of July" that there would be a good chance that somebody else would also have the fifth of July for a birthday; clearly wrong. On the other hand, I'm not defending psychic showmen. We used to consider them a branch of magic, which is not at all due to strange forces, spirits, etc. Although magicians seldom used to state publicly that their acts are just illusions, they do know that, and generally frown on people who use similar techniques to exploit public gullibility. Dunninger is probably turning over in his grave..
weemba@brahms.BERKELEY.EDU (Wimpy Math Grad Student) (07/05/86)
>Gee, weemba, I surprised you didn't also notice that Friesen >misapplied the 23-birthday principle. Gee, gwyn, Friesen only said it analogous, which I interpreted as meaning the operating principle behind the trick was the unexpectedly high odds. ucbvax!brahms!weemba Wimpy Grad Student/UCB Math Dept/Berkeley CA 94720
tedrick@ernie.Berkeley.EDU (Tom Tedrick) (07/06/86)
>>Gee, weemba, [ ... ] >Gee, gwyn, [ ... ] It looks like I finally found a group Gwyn participates in. Now if I can just get him to talk about privatization of educational systems ... I finally found something we agree on but he hasn't responded to my pleas to discuss his ideas ...
rb@cci632.UUCP (Rex Ballard) (07/12/86)
In article <14715@ucbvax.BERKELEY.EDU> weemba@brahms.BERKELEY.EDU (Wimpy Math Grad Student) writes: >In article <1314@psivax.UUCP> friesen@psivax.UUCP (Stanley Friesen) writes: >> Take a group of about >>20 people, what do you think the chances of two of them having the >>same birthday are? In point of fact, it is virtually certain that >>there will be at least one such pair! > >Uh, not exactly. Here's a list of some of the probabilities of a match: > >23: 0.5073 32: 0.7533 41: 0.9032 50: 0.9704 57: 0.9901 > Now what are the odds that one other person would have the same birthday as me? What were the odds that the speaker, and one of those in the audience would have the same thought? The trick here is that both have a "context", earlier speakers for example, which will subconciously guide them to extend into the same thought. The question is HOW?
weemba@brahms.BERKELEY.EDU (Wimpy Math Grad Student) (07/17/86)
In article <215@cci632.UUCP> rb@ccird1.UUCP (another Rochester dummy) writes: >Now what are the odds that one other person would have the same >birthday as me? With N other people, assuming uniform distribution and ignoring leap years, the probability of one match is clearly 1-(364/365)**N. > What were the odds that the speaker, and one >of those in the audience would have the same thought? Huh? What does this have to do with MY posting? ucbvax!brahms!weemba Wimpy Grad Student/UCB Math Dept/Berkeley CA 94720