题目
题型:不详难度:来源:
A.3 | B.9 | C.27 | D.无法确定 |
答案
. |
x |
. |
x |
∵S2=
1 |
n |
. |
x |
. |
x |
. |
x |
=3,
∴方差为S′2=
1 |
n |
. |
x |
. |
x |
. |
x |
=
1 |
n |
. |
x |
. |
x |
. |
x |
=3×9
=27.
故选:C.
核心考点
举一反三
甲:9,10,11,12,7,13,10,8,12,8.
乙:8,13,12,11,10,12,7,7,9,11.
经过计算得:
. |
x甲 |
. |
x乙 |
A.3 | B.9 | C.27 | D.无法确定 |
. |
x |
. |
x |
1 |
n |
. |
x |
. |
x |
. |
x |
1 |
n |
. |
x |
. |
x |
. |
x |
1 |
n |
. |
x |
. |
x |
. |
x |
. |
x甲 |
. |
x乙 |