What is the difference between Variance and Covariance?

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Discussion Overview

The discussion centers on the differences between variance and covariance, focusing on their definitions and applications in statistics. Participants seek clarification and examples to better understand these concepts.

Discussion Character

  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant states that "variance" applies to a single random variable, while "covariance" applies to two or more related random variables.
  • Another participant requests examples to illustrate the concepts of variance and covariance.
  • A later reply provides mathematical definitions for variance and covariance, using random variables X and Y, and includes the formulas for each.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the examples or further explanations, as multiple requests for clarification remain unaddressed.

Contextual Notes

The discussion includes mathematical definitions but does not resolve potential ambiguities in the application of these concepts or the assumptions underlying the examples provided.

DUET
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Could someone please explain it to me what is the difference between Variance and Covariance?
 
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"Variance" applies to a single random variable. "Covariance" applies to two or more related random variables.
 
Could you please give me an example?
 
DUET said:
Could you please give me an example?

Let X and Y be random variables.

var(X) = E(X2) - E(X)2

cov(XY) = E(XY) - E(X)E(Y)

E(..) means average.
 

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