dse 2010

[chhavigupta]

i have a doubt in the following question

Q. a number say X1 is chosen at random from the set (1,2). Then a number say X2 is chosen from the set (1,X1). the probability that X1=2 given that X2=1 is
A 1
B 1/2
C 1/3
D 1/4
 give me a hint to solve this..

[anon_econ]

Hint: P(X1=1, X2=1)= 0.5*1, & P(X1=2, X2=1)=0.5*0.5

[divya]

pls smbdy give a full solutn to this questn.....even i have a prob in this questn

[Shalini Thakur]

Hi this question has already been solved.:)
http://discussion-forum.2150183.n2.nabble.com/DSE-2010-Q-1-td6411727.html;cid=1312299727920-957

[duck]

hi.. :)

Just use the Bayes Rule to get the required probability>

P(X1=2 given that X2=1)= P(X1=2)*P(X2=1 given that X1=2)
                                  ------------------------------------
                                P(X1=2)*P(X2=1 given that X1=2) + P(X1=1)*P(X2=1 given that X1=1)

                                 = 1/3