QCE Vault / Mathematical Methods Discrete random variables — Question 268 Original QCE Vault practice · 1 mark
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QUESTION 268 A player takes four independent shots, each successful with probability 0.6 0.6 0.6 . A badge is awarded for at least three successes. The probability of a badge is WORKED SOLUTION
Answer A 1 mark Worked solution
P ( X ≥ 3 ) = ( 4 3 ) ( 0.6 ) 3 ( 0.4 ) + ( 0.6 ) 4 = 0.4752 P(X\geq3)=\binom43(0.6)^3(0.4)+(0.6)^4=0.4752 P ( X ≥ 3 ) = ( 3 4 ) ( 0.6 ) 3 ( 0.4 ) + ( 0.6 ) 4 = 0.4752 . Exact answers unless rounding is specified; equivalent forms accepted.
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