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Normally distributed and uncorrelated does not imply independent

24 pointsby 666_howitzerabout 10 years ago

6 comments

ishaduaabout 10 years ago
True. Normal distribution is a way a set of data is distributed. That can never imply independance. Think about a scenario: there is no correlation between growth in sales revenue and growth in website traffic. But that does not mean that the two datasets are independant.
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crimsonalucardabout 10 years ago
The Pearson correlation coefficient indicates the strength of a linear relationship between two variables, but its value generally does not completely characterize their relationship.<p>While independence refers to every relationship between two variables, when we use correlation we&#x27;re usually only referring to one type of relationship, a linear relationship.
graycatabout 10 years ago
Uncorrelated and <i>jointly</i> normally Gaussian distributed implies independent. As I recall, there is a careful proof in one of Feller I or II.
thearn4about 10 years ago
The classic standard normal + chi-squared example is also one worth remembering:<p>Let X ~ N(0, 1), and Y = X^2.<p>Cov(X,Y) = 0, though they&#x27;re obviously not independent.
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hammockabout 10 years ago
Can someone provide a real-life example of a data set that this warning applies to?
qmalxpabout 10 years ago
Not a normally distributed example, but:<p>(1,1), (0,0), (1,-1)<p>X and Y are uncorrelated but not independent.
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