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A die is rolled nine times and the number of times that two shows on the upper face is counted. If this experiment is repeated many​ times, find the mean for the number of twos.

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MrRoyal

Answer:

[tex]E(x) = 1.5\\[/tex]

Step-by-step explanation:

Given

[tex]n = 9[/tex] -- number of rolls

Required

The mean of 2's

The distribution follows binomial distribution where:

[tex]X \to Binomial(n,p)[/tex]

In this case:

[tex]p= \frac{1}{6}[/tex] ---- the theoretical probability of rolling 2

So, the mean of 2's is calculated using:

[tex]E(x) = np[/tex]

[tex]E(x) = 9 * \frac{1}{6}[/tex]

[tex]E(x) = \frac{9}{6}[/tex]

Simplify

[tex]E(x) = \frac{3}{2}[/tex] or

[tex]E(x) = 1.5\\[/tex]

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