A pet shop has 9 rabbits for sale, 6 of which are white. A random sample of two rabbits is chosen without replacement.
- Show that the probability that exactly one of the two rabbits in the sample is white is \(\frac{1}{2}\).
- Construct the probability distribution table for the number of white rabbits in the sample.
- Find the expected value of the number of white rabbits in the sample.
Solution
(i) The probability that exactly one rabbit is white can be calculated by considering two cases: one white and one non-white rabbit.
Case 1: First rabbit is white, second is non-white: \(\frac{6}{9} \times \frac{3}{8}\).
Case 2: First rabbit is non-white, second is white: \(\frac{3}{9} \times \frac{6}{8}\).
Adding these probabilities gives: \(\frac{6}{9} \times \frac{3}{8} + \frac{3}{9} \times \frac{6}{8} = \frac{1}{2}\).
(ii) The probability distribution table is constructed as follows:
| x | 0 | 1 | 2 |
|---|
| Prob | \(\frac{1}{12}\) | \(\frac{1}{2}\) | \(\frac{5}{12}\) |
(iii) The expected value \(E(X)\) is calculated as:
\(E(X) = 0 \times \frac{1}{12} + 1 \times \frac{1}{2} + 2 \times \frac{5}{12} = \frac{16}{12} = \frac{4}{3}\).
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