更新时间2019-01-06 22:10:37
平均数:
(3x₁-2+3x₂-2+.......3xn-2)/n
=3(x₁+x₂+.......+xn)-2n/n
=3(x₁+x₂+......+xn)/n-2
=3×2-2
=4
方差:
S²=[(3x₁-2-4)²+(3x₂-2-4)²+.........+(3xn-2-4)²]/n
=[(3x₁-6)²+(3x₂-6)²+.........+(3xn-6)²]/n
=9[(x₁-2)²+(x₂-2)²+........+(xn-2)²]/n
=9×1/3
=3
平均数是4.方差是9.