Probability 3 Question 6

6. Let two fair six-faced dice A and B be thrown simultaneously. If E1 is the event that die A shows up four, E2 is the event that die B shows up two and E3 is the event that the sum of numbers on both dice is odd, then which of the following statements is not true?

(2016 Main) (a) E1 and E2 are independent

(b) E2 and E3 are independent

(c) E1 and E3 are independent

(d) E1,E2 and E3 are independent

Show Answer

Solution:

  1. Clearly, E1=(4,1),(4,2),(4,3),(4,4),(4,5),(4,6)

and $\quad \begin{aligned} E _2 & ={(1,2),(2,2),(3,2),(4,2),(5,2),(6,2)} \ E _3 & ={(1,2),(1,4),(1,6),(2,1),(2,3),(2,5),\end{aligned}$

(3,2),(3,4),(3,6),(4,1),(4,3),(4,5), Extra close brace or missing open brace

P(E1)=636=16,P(E2)=636=16

and P(E3)=1836=12

Now, P(E1E2)=P (getting 4 on die A and 2 on die B )

=136=P(E1)P(E2)

P(E2E3)=P (getting 2 on die B and sum of numbers on both dice is odd)

=336=P(E2)P(E3)

P(E1E3)=P (getting 4 on die A and sum of numbers on both dice is odd)

=336=P(E1)P(E3)

and P(E1E2E3)=P [getting 4 on die A,2 on die B and sum of numbers is odd]

=P( impossible event )=0

Hence, E1,E2 and E3 are not independent.



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