jimmyc99

84595. Tue Aug 08, 2006 1:22 pm 


grizzly wrote:  jimmyc99 wrote:  dr.bob wrote:  Could someone please mention to the BBC that I'm going to be on holiday in Italy for the first 2 weeks in September. So, if they're going to start showing the D series in september, can someone politely ask them to wait until I get back? 
that's no good as I am on holiday from 3rd week in September until 4th week in October so they will need to delay transmission until early November which probably means the Christmas special will be broadcast in February... 
Where are you going for such a long holiday? 
We are touring around SW USA  Sequoia Nat Park, Death Valley, Grand Canyon, Vegas, Monument Valley, Petrified Forest, Joshua Tree.
It's a trip I have been meaning to take for the last few years but finally everything has come together so I guess missing 3 QI episodes won't be the end of the world... 




grizzly

84600. Tue Aug 08, 2006 1:31 pm 


If you're going to miss QI at least do something useful with your time like learning something. I think your holiday fulfills that Jimmy. 




Hans Mof





grizzly

84610. Tue Aug 08, 2006 1:49 pm 


No you're wrong. That is the probability for a group of 23 people or more (i.e. 23*1in365 as only one of the 23 need share the birthday).
In this case there is only one other person (Ameena). Therefore the probability of Ameena sharing the same birthday is 1 in 365.
If you were to ask, what is the probability that someone else on the forum shares the same birthday then the probability will be 100%.
Edit: Also take account of the fact that in this problem in particular (where 23 people are given) remember that it is only one person of any of the 23 having the same birthday of any of the other 22. This is not the case here as it is specified that it is No1 who is the person who should share the birthday with someone else.
Nice that you should bring up the birthday paradox though. 




Hans Mof

84613. Tue Aug 08, 2006 1:57 pm 


You have a point there. With only two persons the probability will of course only be 0.0027397260274%. Nevertheless, since Ameena was born in a leap year this needs to be slightly adjusted.
Edit:
A birthday paradox calculator (sorry, only in German)
[img]http://www.mathematik.ch/anwendungenmath/wkeit/geburtstag/[/img]
Edit: The percentage above should of course read 0.27397260274%
I have no idea, who put the 00 in there. ;) Last edited by Hans Mof on Tue Aug 08, 2006 7:14 pm; edited 1 time in total





Celebaelin

84615. Tue Aug 08, 2006 2:10 pm 


Hans Mof wrote:  You have a point there. With only two persons the probability will of course only be 0.0027397260274%. 
Nope, wrong again!
0.27397etc%
roughly 1 in 400 you see? 




grizzly

84617. Tue Aug 08, 2006 2:30 pm 


Of course if you took 2 random peaople off of the street and wanted to know the probability that both of their birthdays were on the 1st January it would be 0.0000075061 (1 in 133225) since you don't know the birthday of either of them. 




jimmyc99

84635. Tue Aug 08, 2006 3:03 pm 


All of the above assumes that dates of birth are evenly distributed throughout the year.
Is that the case? I would suspect there is a peak roughly 9 months after those cold winter evenings? 




Celebaelin





Andrew

84645. Tue Aug 08, 2006 3:48 pm 


I was about to reply to various messages here but I see no point now as everything I was going to say has already been said  I must not be sociable when my aunt and uncle come round...MUST read QI forum :D 




grizzly

84655. Tue Aug 08, 2006 4:20 pm 


BTW, I hope the news on D series goes up on the front page soon. 




suze

84667. Tue Aug 08, 2006 5:40 pm 


Neither am I. But I did go so far as to paste that data into a spreadsheet and then order it by frequency.
Seven of the eleven most common dates of birth in that year fell in September. Bearing in mind that the data relate to the USA, the Thanksgiving holiday (late November in the USA) is likely implicated as well as Christmas.
Otherwise, July and August seem to be common birth months. Again given that we are talking Americans, there may be an element of deliberate family planning to produce offspring to arrive in the warmest months of the year.
April appears to be the month when people don't get born  five of the ten lowest scores were for April dates. I do not attempt to offer an explanation for this. 




samivel

84674. Tue Aug 08, 2006 6:29 pm 


I do  all American wouldbe parents are scared that T.S. Eliot was right. That's a fact, that is. 




grizzly

84704. Wed Aug 09, 2006 2:28 am 


Thanks giving? Those dates beter be at the very start of the month because I don't think it would be likely that 10 month pregnancies would have much of an effect on the figures (since most would be induced after 9 months and 2 weeks). 




suze

84709. Wed Aug 09, 2006 3:38 am 


They were indeed  the first and last weeks of September showed the highest incidence of birth.
Apart from April indeed being the cruellest month, I still have no idea why those Americans didn't seem inclined to get down to serious baby making in July 1977 ... 



