Question

Two coins are to be flipped. The first coin will land on heads with probability 0.6, the second with probability 0.7. Assume that the results of the flips are independent, and let X equal the total number of heads that result. (a) Find P{X=1}. (b) Determine E[X].

Answer 1

Step-by-step explanation:

P(X=1)  = P(first heads and second tails) +P(first tails and second heads)

            =P(first heads)×P(second tails)    +  P(first tails)  ×P(second heads)              

             because events are independent P(A∩B)  = P(A) ×P(B)

            = 0.6 ×0.3 + 0.4 ×0.7

            = 0.46

P(X=0)    = P(first tails and second tails)

               = 0.4  ×0.3

               =0.12

P(X=2)    =   P(first heads and second heads)

               = 0.6 ×0.7

               = 0.42

Mean   E(X)     =    0 ×0.12 + 1 × 0.46 + 2 ×0 0.42

                        =1.3            ( Because mean is ratio it can can be greater than 1 )