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Mathematical Methods Β· Unit 3 Β· Discrete random variables Β· General discrete random variables

Determine and use the variance of a discrete random variable as a measure of spread, π‘‰π‘Žπ‘Ÿ (𝑋) = βˆ‘ 𝑝𝑖 (π‘₯𝑖 βˆ’ πœ‡)2 where 𝑝𝑖 is the probability of outcome π‘₯𝑖 occurring, πœ‡ is the mean.

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Question 1

A discrete random variable X has a probability distribution with mean ΞΌ = 3.2 and E(XΒ²) = 11.8. Explain what the variance of X measures in the context of this distribution, and determine its value.

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Question 2

Consider the Bernoulli distribution where the outcomes for rolling a standard die are obtaining a five and not obtaining a five. Determine the variance of the resulting Bernoulli distribution in this scenario.

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Question 3

A discrete random variable $X$ represents the number of faulty items in a sample of 5 products from a manufacturing line. The probability distribution is given in the table below. Determine the variance of $X$, correct to 2 decimal places.

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Question 4

A discrete random variable $X$ represents the number of defective items in a batch of 5 items. The probability distribution is given in the table below. Determine the variance of $X$, giving your answer correct to 2 decimal places.

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