Simple statistics expectation calculation

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SUMMARY

This discussion focuses on calculating the expectation of a random sample from a normal distribution with a known mean (μ) and unknown variance (σ²). The key equation presented is E(n/2θ² - ∑(xi-μ)/2θ³), where θ is set to σ². The conclusion is that the expectation simplifies to n/2θ², with the second term equating to zero due to the properties of expectations of random variables. Participants also clarify the distinction between expectations of random variables and their corresponding values.

PREREQUISITES
  • Understanding of normal distribution and its parameters (mean μ and variance σ²).
  • Familiarity with the concept of expectation in probability theory.
  • Knowledge of random variables and their properties.
  • Basic calculus for manipulating equations involving expectations.
NEXT STEPS
  • Study the properties of expectations in probability theory.
  • Learn about the Central Limit Theorem and its implications for sampling distributions.
  • Explore the derivation of the expectation for functions of random variables.
  • Investigate the use of moment-generating functions in calculating expectations.
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Students and professionals in statistics, data science, and quantitative research who are looking to deepen their understanding of expectation calculations in probability theory.

missavvy
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Homework Statement



I am just trying to figure out how to calculate the expectation of something.
The context is for a random sample from a normal distribution with known mean μ and unknown variance σ2.

Homework Equations


3. The solution

So for the purposes of this question we set θ = σ2
I want to calculate:

-E(n/2θ2 - \sum(xi-μ)/2θ3)

The answer ends up being just n/2θ2
Why is the second term 0?

Also if anyone has any links or notes about expectation of values similar this, for example, that would be great.
Thanks
 
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missavvy said:

Homework Statement



I am just trying to figure out how to calculate the expectation of something.
The context is for a random sample from a normal distribution with known mean μ and unknown variance σ2.

Homework Equations





3. The solution

So for the purposes of this question we set θ = σ2
I want to calculate:

-E(n/2θ2 - \sum(xi-μ)/2θ3)

The answer ends up being just n/2θ2
Why is the second term 0?

Also if anyone has any links or notes about expectation of values similar this, for example, that would be great.
Thanks

What are the values of E(X1-μ), E(X2 - μ), etc.?

BTW: it is customary in Probability discussions to use a capital letter to stand for a random variable and the corresponding small letter to stand for a possible value; so x is a possible value of the random variable X, and you are sampling from a multi-dimensional random variable (X1, X2, ... Xn). Talking about E(X-μ) is different from talking about E(x-μ): one of them is the expectation of a random variable, while the other is the expectation of a non-random number (which of course, is just that number itself).

RGV
 
It would be
Ʃ (E(Xi) - μ) = 0
?

How would I calculate E(1/2θ3) ? (I know I wouldn't need to here since it's 0 on top, but just out of curiosity)
 

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