问题 填空题

变量x与y具有线性相关关系,当x取值为16,14,12,8时,通过观测得到y的值分别为11,9,8,5.若在实际问题中,y的预报值最大是10,则x的最大取值不能超过________.

答案

15

由题中数据可求得线性回归方程为=0.729x-0.857,当=10时,x≈14.89≈15,

∵0.729>0,

∴当y的预报最大取值为10时,x的最大取值不能超过15.

阅读理解

根据短文内容,选择最佳答案。

    Every town in the United States has a post office. Some are very smalll, and you may find one in the corner

of a shop.Others are large buildings. They are open five days a week from Monday through Friday. They are

usually open from 8:30am to 4:30 pm.

    if you know how much the postage (邮资) is for your letter, you can buy stamps at any window. In some

post offices you can buy stamps from machines. Stamps are sold at many different prices. From one cent to

many dollars. If you are not sure how much postage (邮资) is for your letter, you may ask the man or the

woman in the post office for help.He or she will give you the stamps you need. If you are sending your letters

far away, you shall use airmail envelopes (航空信封). Remember that postage (邮资) will be more expensive for

a letter to be sent outside the country.

    At a post office you can also buy postcards. A postcard is cheaper than a letter. Usually the price of postage

(邮资) for a postcard is about half that of a letter. The postcards, however, are not to be sent outside the

country.

    Letters are an easy and cheap way to keep in touch with people in many different countries.

1. The passage tells us that we can find _______ easily in the United States.[ ]

A. post offices

B. large buildings

C. small shops

D. different banks

2. The post offices in the United States are open _______ a day. [ ]

A. seven hours

B. six hours

C. five hours

D. eight hours

3. If you are not sure how much postage (邮资) is for your letter, you can _______. [ ]

A. go and buy stamps from the machine in the post office

B. send a cheap postcard instead of your letter

C. get in touch with someone you know in the post office

D. ask the man or the woman in the post office for help.

4. The price of postage (邮资) for _______ is more expensive. [ ]

A. a beautiful postcard

B. a letter written on envelope

C. a letter by airmail

D. a postcard with pictures

5. The passage tells us something about               in the USA. [ ]

A. the post

B. the postage (邮资)

C. letters

D. postcards

名词解释