Find mean and variance of X and Y

In summary, the individual is asking for guidance on finding the mean, variance, and correlation coefficient for X and Y from a given table. They have calculated the means for X and Y, but are unsure if they are correct. The correct formula for finding the mean of a random variable is also provided.
  • #1
phillyolly
157
0

Homework Statement



I have found the marginal distribution for X and Y from a table. (No statistical regression, just simple table)
How should I proceed in finding mean, variance an correlation coefficient of X and y? I am computing by hand.
Thank you,



Homework Equations





The Attempt at a Solution

 

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  • #2
Is mean for X:

(1/8+3/8+3/8+1/8)
-------------------
4

and mean for Y is

(2/8+4/8+2/8)
--------------
3

?
 
  • #3
No. Remember the mean of a random variable is defined as

[tex]\bar{X} = \sum_i x_i P_X(x_i)[/tex]

It's the sum of the product of the values X can take on multiplied by probability of that value.
 

What is the formula to find the mean of X and Y?

The mean of a set of numbers can be calculated by summing all the numbers and dividing by the total number of numbers in the set. In the case of X and Y, the formula would be:
Mean of X = (x1 + x2 + ... + xn) / n
Mean of Y = (y1 + y2 + ... + yn) / n

How do I find the variance of X and Y?

The formula to find the variance of a set of numbers is:
Variance = ((x1 - mean)^2 + (x2 - mean)^2 + ... + (xn - mean)^2) / n
For X and Y, the variance would be calculated separately using the mean of X and Y.

What is the difference between mean and variance?

Mean is a measure of central tendency that represents the average value of a set of numbers. It is calculated by adding all the numbers in the set and dividing by the total number of numbers. Variance, on the other hand, measures the spread or variability of the numbers in a set. It is calculated by finding the average of the squared differences between each number and the mean. In simpler terms, mean tells us the typical value of a set, while variance tells us how much the numbers deviate from that typical value.

Can the mean and variance of X and Y be the same?

Yes, it is possible for the mean and variance of X and Y to be the same. This would happen if all the numbers in the set have the same value. In this case, the mean and variance would both be equal to that value.

Why do we need to calculate the mean and variance of X and Y?

Calculating the mean and variance of X and Y can help us better understand the data and make statistical inferences. The mean gives us a general idea of the typical value of the set, while the variance tells us how much the numbers vary from that typical value. These measures are commonly used in various fields, including science, economics, and social sciences, to analyze and interpret data.

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