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June 2023 p51 q6
2974
Eli has four fair 4-sided dice with sides labelled 1, 2, 3, 4. He throws all four dice at the same time. The random variable X denotes the number of 2s obtained.
(a) Show that \(P(X = 3) = \frac{3}{64}\).
(b) Complete the following probability distribution table for \(X\).
x
0
1
2
3
4
P(X = x)
\(\frac{81}{256}\)
\(\frac{3}{64}\)
\(\frac{1}{256}\)
(c) Find \(E(X)\).
Solution
(a) To find \(P(X = 3)\), we use the binomial probability formula: