问题 解答题

为备战2012年伦敦奥运会,甲、乙两位射击选手进行了强化训练.现分别从他们的强化训练期间的若干次平均成绩中随机抽取8次,记录如下:

甲:8.3  9.0  7.9  7.8  9.4  8.9  8.4  8.3;

乙:9.2  9.5  8.0  7.5  8.2  8.1  9.0  8.5.

(Ⅰ)现要从中选派一人参加奥运会封闭集训,从统计学角度,你认为派哪位选手参加合理?简单说明理由;

(Ⅱ)若将频率视为概率,对两位选手在今后各自的二次比赛成绩进行预测,求这四次成绩中恰有两次不低于8.5分的概率.

答案

(Ⅰ)可计算出

.
x
=8.5,
.
x
=8.5.

S2=

1
8
[0.04+0.25+0.36+0.49+0.81+0.16+0.01+0.04]=
2.16
8
=0.27.

S2=

1
8
[0.49+1+0.25+1+0.09+0.16+0.25+0]=
3.24
8
=0.405.

故甲、乙两位射击选手的水平相当,但甲的发挥更稳定一些,故选择甲去.

(Ⅱ)甲的成绩不低于8.5的概率为p1=

3
8
,乙的成绩不低于8.5的概率为p2=
4
8
=
1
2

于是所求概率等于

C12
3
8
5
8
×
C12
1
2
1
2
+(
3
8
)2×(
1
2
)2+(
5
8
)2×(
1
2
)2=
60+9+25
64×4
=
47
128

所以,这四次成绩中恰有两次不低于8.5的概率为

47
128

阅读理解

下面文章中有5处需要添加小标题。请从以下选项(A、B、C、 D、E 和 F)中选出符合各段意思的小标题,并在答题纸上将相应选项的标号涂黑。选项中有一项是多余选项。

Tips for

Being a Good Neighbor

小题1:_______________

No one likes a noisy neighbor. Do you hold parties that last all night? Do you leave your dog outside to bark all day? Remember that not everyone has the same schedule as you do, so use some common sense. Keep noise to the lowest level. If you’re holding a party that’s likely to be loud, invite everyone within earshot(听力范围)。

小题2:________________

It’s much easier to solve any problem with neighbors if you have a friendly relationship with those around you. Furthermore, you may realize that you have things in common and make a lifelong friend.

小题3:_________________

Once you know your neighbors, then you’ll also know if something seems out of place in the neighborhood. Are strange people carrying expensive things out of one neighbor’s house? Have several days passed since your elderly neighbor last collected his newspaper? The benefit of keeping an eye out for unusual behavior in the neighborhood is that others will do the same for you.

小题4:___________________

It never hurts to follow the Golden Rule: Do to others what you would like them to do to you. Treat your neighbors with respect. Offer to drive an elderly neighbor to the grocery store. Volunteer to collect mail while a neighbor is on vacation. The more often you lend a helping hand, the more likely that your neighbors will do the same for you when you need a little help.

小题5:_____________________

Don’t just limit your neighborly actions to your block or street. Remember that everyone who lives in a community has the ability to help make it a better place. Think about your passion and find a way to do it on a volunteer basis in your town. Volunteer at the local library. Enjoy working with kids. Consider becoming a scout (童子军)leader. Whatever your passion is, there’s sure to be a thing suitable for you to help in the local community.

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