∑ i  ( F i     2     )  ( ( F ¯  i     2     )  − ∑ j ≠ i   ( F j     2     )     )    ,       ( 13  )    MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=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@4E95@