NETMaths

Is this true?

If X and Y are each normal and uncorrelated then they are independent

No — it is false.

The counterexample

X ~ with probability ½ independent of

Y is N(0,1), Cov(X,Y) = 0, but |X| = |Y| always. The pair is not jointly normal.

The kind of mistake this is

Dependence misread

Independence, pairwise vs mutual, or correlation vs dependence.

Drill statements like this

Others that fail the same way

From ProbabilityJoint distributions, transformations, order statistics

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