[BNM] [OT] Lottery puzzle

['Alex' Bridge]

Buying 2 tickets in one draw is betting on two mutually exclusive 
outcomes i.e. only one ticket can win the jackpot, so the probabilities 
are simply additive.

Buying 2 tickets for different draws is betting on two independent 
outcomes i.e. both could potentially win the jackpot, so the probability 
of this needs to be accounted for when working out the probability of 
one of them winning.

For mutually-exclusive outcomes, probability of A or B is P(A)+P(B)
For independent outcomes, probability of A or B is P(A)+P(B) - P(A and B)

So buying on different draws is always going to be P(A and B) less than 
buying them for a single draw.

-alx


Also sprach James Cline:
> I believe that the maths is simply 57/14000000 if you spend 57 all on one
> draw compaired with 1/14000000 if you played over 57 draws.
> It doesn't matter how many times you play because each draw the numbers will
> be different so there is still only 1 in 14000000. Your chances of winning
> do not increase. 
>
> James
>
>
>
>
> On 24/09/2008 12:20, "David Pashley" <david at davidpashley.com> wrote:
>
>   
>> On Sep 24, 2008 at 11:41, Julian Blundell praised the llamas by saying:
>>     
>>> Got very board with this line, read this
>>>
>>> http://www.bbc.co.uk/dna/h2g2/A2390032
>>>
>>> Jules
>>>
>>>       
>> Still fails to prove it with maths. Does no one have a link with a
>> correct mathematical proof?
>>     
>
>
>   


-- 
Views or opinions expressed in this email are not necessarily 
those of the author and are not guaranteed fit for purpose.
Not suitable for children under 36 months. May contain nuts.