SOLUTION: Let x be a random variable that denotes the number of tails obtained when three coins are tossed? a. Find E(X) = ........ I solved this one, 1.5 b. Find the P(x < or = to 2)

Algebra ->  Probability-and-statistics -> SOLUTION: Let x be a random variable that denotes the number of tails obtained when three coins are tossed? a. Find E(X) = ........ I solved this one, 1.5 b. Find the P(x < or = to 2)      Log On


   

Question 1174544: Let x be a random variable that denotes the number of tails obtained when three coins are tossed?
a. Find E(X) = ........ I solved this one, 1.5
b. Find the P(x < or = to 2) for the random variable
c. Find the P(x<5) for the random variable
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!

Hi
 P+%28x%29=+highlight_green%28nCx%29%28p%5Ex%29%28q%29%5E%28n-x%29+ Binomial Theorem
       N = 3 coins tossed               p(H)=1/2   and q(T)=1/2 

 P(x ≤ 2) = P(x=0) + P(x=1) + P(x=2)
P(x=0) + P(x=1) + P(x=2) = 3C0(1/2^)3 + 3C1(1/2)^3 + 3C2(1/2)^3 
     (1/8) + (3/8) + (3/8)  = .875

  P(x < 5) = 1   
 NOte: P(x=0) + P(x=1) + P(x=2) + P(x=3) = .875 + .125 = 1

Wish You the Best in your Studies.