Question:

A random variable X has the probability distribution
\(X = x\)\(1\)\(2\)\(3\)\(4\)\(5\)\(6\)\(7\)\(8\)
\(P(X = x)\)\(0.23\)\(0.15\)\(0.12\)\(0.10\)\(0.20\)\(0.07\)\(0.08\)\(0.05\)

for the events E = {X is a prime number} and F = {X \(\leq\) 3}, then P (E\(\cup\)F)=

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Use P(E union F) = P(E) + P(F) - P(E and F).
Updated On: Oct 1, 2026
  • \(0.55\)
  • \(0.70\)
  • \(0.87\)
  • \(0.78\)
Show Solution
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The Correct Option is D

Solution and Explanation

Step 1: Understanding the Concept:
\(E = \{2, 3, 5, 7\}\) (primes) and \(F = \{1, 2, 3\}\) (\(X \le 3\)). Read the probabilities from the table.

Step 2: Compute each part:
\(P(E) = 0.15 + 0.12 + 0.20 + 0.08 = 0.55\).
\(P(F) = 0.23 + 0.15 + 0.12 = 0.50\).
\(E\cap F = \{2, 3\}\), so \(P(E\cap F) = 0.15 + 0.12 = 0.27\).

Step 3: Apply the formula:
\[ P(E\cup F) = 0.55 + 0.50 - 0.27 = 0.78 \]

Step 4: Check by listing:
\(E\cup F = \{1, 2, 3, 5, 7\}\): \(0.23 + 0.15 + 0.12 + 0.20 + 0.08 = 0.78\). Option (D).

Final Answer:
P(E or F) = 0.55 + 0.50 - 0.27 = 0.78. \[ \boxed{\text{(D) }0.78} \]
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