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Nov 2019 p62 q5
2901
A fair red spinner has four sides, numbered 1, 2, 3, 3. A fair blue spinner has three sides, numbered -1, 0, 2. When a spinner is spun, the score is the number on the side on which it lands. The spinners are spun at the same time. The random variable X denotes the score on the red spinner minus the score on the blue spinner.
(i) Draw up the probability distribution table for X.
(ii) Find \(\text{Var}(X)\).
Solution
(i) To find the probability distribution of \(X\), calculate \(X = \text{Red} - \text{Blue}\) for all combinations: