Question
Tue May 27, 2008 By:

probability question.

Expert Reply
Thu September 11, 2008

total no. ways of selecting two no.s = 30 ( to select first no. we have 6 options and to select second no. we have 5 options)

P(X=1) =0   (since any no. which is choosen with 1 will be the largest)

P(X=2) =2*1/30  ( when 1 is selected with 2 )

P(X=3) =2*2/30  ( when 1 or 2 is selected with 3 )

P(X=4) =2*3/30  ( when 1 or 2 or 3 is selected with 4 )

P(X=5)=2*4/30   ( when 1 or 2 or 3 or 4 is selected with 5 )

P(X=6) =2*5/30  ( when 1 or 2 or 3 or 4 or 5 is selected with 6 )

here all probabilities are multiplied by 2 because if (1,2) is a valid pair then (2,1) will also be valid

E(X) = summation of (x*P(x) )

        =(4+12+24+40+60)/30 = 140/30 = 4.67

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