Stats Problem about Expectations of Random Variables

In summary, the expectation of a random variable is the average value or mean of all possible outcomes of the variable. It is calculated by multiplying each possible outcome by its probability and then summing up all the products. This differs from its actual values, which are the specific outcomes that may vary from trial to trial. The expectation of a random variable can be negative, indicating that the average outcome is lower than the expected value. To calculate the expectation of a discrete random variable, you multiply each possible outcome by its probability and sum the products. For continuous random variables, the expectation is calculated by integrating the product of the variable and its probability density function over its entire range.
  • #1
hjqusai
3
0

Homework Statement



Let X have mean u and variance s^2. Find the mean and the variance of Y=[(X-u)/s]

Homework Equations


The Mean is linear

The Attempt at a Solution


I thought to just plug in the mean of X anywhere i saw it in Y so mean of Y would be 0
and then for the variance I was kind of lost... Any suggestions?
 
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  • #2
Remember

[tex]
\begin{align*}
E(aY+b) &= aE(Y)+ b\\
Var(aY) & = a^2 Var(Y)
\end{align*}
[/tex]
 
  • #3
Didn't know that second formula. Thanks for your help!
 

FAQ: Stats Problem about Expectations of Random Variables

1. What is the definition of expectation of a random variable?

The expectation of a random variable is the average value or mean of all possible outcomes of the variable. It is calculated by multiplying each possible outcome by its probability and then summing up all the products.

2. How is the expectation of a random variable different from its actual values?

The expectation of a random variable is a theoretical value that represents the average outcome, while the actual values are the specific outcomes that may vary from trial to trial.

3. Can the expectation of a random variable be negative?

Yes, the expectation of a random variable can be negative. This means that the average outcome is lower than the expected value.

4. How do you calculate the expectation of a discrete random variable?

The expectation of a discrete random variable is calculated by multiplying each possible outcome by its probability and then summing up all the products. Mathematically, it can be represented as E(X) = ΣxP(x), where X is the random variable and P(x) is the probability of the outcome x.

5. Can the expectation of a continuous random variable be calculated using the same formula as a discrete random variable?

No, the expectation of a continuous random variable cannot be calculated using the same formula as a discrete random variable. For continuous random variables, the expectation is calculated by integrating the product of the variable and its probability density function over its entire range. Mathematically, it can be represented as E(X) = ∫xf(x)dx, where X is the random variable and f(x) is its probability density function.

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