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Feb/Mar 2017 p62 q3
3305
It is found that 10% of the population enjoy watching Historical Drama on television. Use an appropriate approximation to find the probability that, out of 160 people chosen randomly, more than 17 people enjoy watching Historical Drama on television.
Solution
Let the random variable \(X\) represent the number of people who enjoy watching Historical Drama. \(X\) follows a binomial distribution with parameters \(n = 160\) and \(p = 0.1\).
We approximate this binomial distribution with a normal distribution. First, calculate the mean \(np\) and variance \(npq\):
\(np = 160 \times 0.1 = 16\)
\(npq = 160 \times 0.1 \times 0.9 = 14.4\)
Using the normal approximation, we have \(X \sim N(16, 14.4)\).
We need to find \(P(X > 17)\). Using continuity correction, this is \(P(X \geq 17.5)\).