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Nov 2016 p61 q3
3066
Visitors to a Wildlife Park in Africa have independent probabilities of 0.9 of seeing giraffes, 0.95 of seeing elephants, 0.85 of seeing zebras and 0.1 of seeing lions.
Find the probability that a visitor to the Wildlife Park sees all these animals.
Find the probability that, out of 12 randomly chosen visitors, fewer than 3 see lions.
50 people independently visit the Wildlife Park. Find the mean and variance of the number of these people who see zebras.
Solution
(i) The probability that a visitor sees all the animals is the product of the individual probabilities:
(ii) Let the random variable \(X\) be the number of visitors who see lions. \(X\) follows a binomial distribution \(X \sim B(12, 0.1)\). We need to find \(P(X < 3)\), which is \(P(0) + P(1) + P(2)\).
(iii) Let \(Y\) be the number of people who see zebras. \(Y\) follows a binomial distribution \(Y \sim B(50, 0.85)\). The mean \(E(Y)\) is given by \(np\) and the variance \(Var(Y)\) is given by \(np(1-p)\).