1.

A random variable X has the following probability distribution:X:12345678P(X):0.150.230.120.100.200.080.070.05For the events E = {X : X is a prime number}, F = {X : X < 4}, the probability P (E ∪ F) isA. 0.50B. 0.77C. 0.35D. 0.87

Answer»

Correct answer is B.

E = (X : X is a prime number)=(2, 3, 5, 7)

P(E) = P(X = 2) + (X = 3) + (X = 5) + (X = 7)

P(E) = 0.23 + 0.12 + 0.20 + 0.07 = 0.62

F=(X : X < 4) = (1, 2, 3)

P(F) = P(X = 1) + (X = 2) + (X = 3)

P(F)= 0.15 + 0.23 + 0.12 = 0.5

E∩F = (X is a prime number as well as < 4) = (2, 3)

P(E∩F) = P(X = 2) + P(X = 3)

⇒ 0.23 + 0.12 = 0.35

P(E∪F) = P(E) + P(F) - P(E∩F)

⇒ 0.62 + 0.50 - 0.35

= 0.77



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