方差的意义!
(2)、(42 + 45 + 48 +46 + 52 + 47+ 49 + 55 + 42 +51 + 47+ 45)/12=-47.41666667
-47.17
(42-47.42)^2 + (45-47.42)^2 + (48-47.17 )^2 +(46-47.17)^2 + (52-47.17)^2 +( 47-47.17)^2
+ ( 49-47.17 )^2+( 55-47.17 )^2+( 42-47.17 )^2 +(51-47.17)^2 + (47-47.17)^2+ (45-47.17)^2
=166.9166667
= (55 + 36 +70 +66 +75 +49 +46 + 68 + 42+ 62 + 58 + 47 )/12=56.16666667
(56.17-55)^2+(36-56.17)^2+(70-56.17)^2+(66-56.17)^2+(75-56,17)^2+(49-56.17)^2+
(46-56.17)^2+(68-56.17)^2+(42-56.17)^2+(62-56.17)^2+(58-56.17)^2+(47-56.17)^2=1667.666667