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55#
发表于 2012-3-22 14:25
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The covariance: A)
| must be between -1 and +1. |
| B)
| can be positive or negative. |
| |
Cov(a,b) = σaσbρa,b. Since ρa,b can be positive or negative, Cov(a,b) can be positive or negative. |
|