Tell me more ×
Cross Validated is a question and answer site for statisticians, data analysts, data miners and data visualization experts. It's 100% free, no registration required.

Given a covariance matrix, it's simple to draw a venn diagram representing the independent and shared variance of two variables. How might one go about the same (at least, computing all pertinent areas; actual visualization not necessary) for the 3-variable case? Is this even possible?

share|improve this question
1  
I'm curious even about the two-variable case. What exactly is "shared variance" when the covariance is negative? – whuber Feb 22 '12 at 14:21
1  
Maybe I'm way off here, but shouldn't it be r^2? – Mike Lawrence Feb 22 '12 at 14:36

1 Answer

A Venn diagram is more of an abstract way of illustrating events and probability space than a real tool.

If you have an experiment where events A and B can occur with some degree of dependence, then you can represent their joint probability distribution using a 2 by 2 table. The "upper left" corner indicates the probability that A and B are observed jointly. This is equivalent to the area of the overlap of the circles.

If there's a third event, C, then you can again represent their joint probability distribution using a 2 by 2 by 2 table. Again, the cell in the 1st table's upper left hand entry should represent the hyperarea of the intersection of probability spheres A, B, and C.

The tabular presentation of data and probability is more relevant to modern statistics whereas the Venn diagram is more of a learning tool for conceptualization.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.