问题 填空题
甲、乙两名学生进行射击练习,两人在相同条件下各射靶10次,将射击结果作统计分析如下:
命中环数5678910
甲命中环数的次数142111
乙命中环数的次数124210
请你从射击稳定性方面评价甲、乙两人的射击水平,则______比较稳定(填“甲”或“乙”).
答案

甲、乙两人射击成绩的平均成绩分别为:

.
x
=(5+4×6+2×7+8+9+10)÷10=7,(2分)

.
x
=(5+2×6+4×7+2×8+9+0)=7,(3分)

S2=【(5-7)2+4(6-7)2+(8-7)2+(9-7)2+(10-7)2】÷10=1.7,(5分)

S2=【(5-7)2+2(6-7)2+2(8-7)2+(9-7)2+0】÷10=1.2(6分)

∵s2>s2

∴乙同学的射击成绩比较稳定.(8分).

故答案为乙.

多项选择题
单项选择题

There (1) not one type of reading but several according to your reasons for reading. To read carefully, you have to (2) your reading speed and technique (3) your aim (4) reading. Skimming is a technique necessary for quick and efficient reading.

When skimming, you (5) the reading (6) quickly in order to get the (7) of it, to know how it is organized, (8) an idea of the tone or the intention of the writer. Skimming is (9) an activity which (10) an overall view of the text and (11) a definite reading competence.

Skimming doesn’t need reading all the material, but it doesn’t mean that it is an (12) skill for the lazy, because it need a high degree of alertness and concentration.

When you read, you usually start with (13) understanding and move towards detailed understanding rather than working the other way round. But (14) is also used after you have already carefully studied and you need to (15) the major ideas and concepts.

In order to be able to skim quickly and (16) through a text, you should know where to look for what you want. In preview skimming you read the introductory information, the headings and subheadings, and the summary, if one is provided. (17) this skimming, decide whether to read the material more thoroughly, and select the appropriate speed (18) you read.

The same procedure (19) for preview skimming could also be used to get an overview. Another method would be to read only key words. This is done by omitting the unnecessary words, phrases, and sentences.

In order to skim efficiently and fulfill your purpose, (20) practice is necessary.

12().

A.awful

B.unsuitable

C.ideal

D.wrong