问题 多项选择题

在组距数列中,关于组中值的表述,下列选项正确的有()。

A.是上限和下限之间的中点数值

B.当各组内标志值均匀分布时,用来代表各组标志值的平均水平

C.在开口组中无法确定

D.在开口组中,可以参照相邻组的组距来确定

E.是该组的上限值

答案

参考答案:A, B, D

解析:组中值是每个组上限与下限的中点值。组中值是代表各组标志值平均水平的数值,当各组内标志值均匀分布时,可用组中值代表各组标志值的平均水平,但当各组标志值不是均匀分布时,组中值只能近似代替各组实际平均值。开口组的组中值可以由下列公式来计算:首组开口组的组中值=首组上限-邻组组距/2,末组开口组的组中值=末组下限+邻组组距/2。

阅读理解

Brownie and Spotty were neighbor dogs who met every day to play together. Like pairs of dogs you can find in any neighborhood, these two loved each other and played together so often that they had worn a path through the grass of the field between their houses.

One evening, Brownie’s family noticed that Brownie hadn’t returned home. They went looking for him with no success. Brownie didn’t show up the next day, and, although they made their efforts to find him, by the next week he was still missing, Curiously, Spotty showed up at Brownie’s house alone, barking and jumping. Busy with their own lives, they paid no attention to the nervous little neighbor dog.

Finally, one morning Spotty refused to take “no” for an answer. Ted, Brownie’s owner, was continuously disturbed by the angry, determined little dog. Spotty followed Ted about, barking all the time, then rushing toward a nearby empty lot and back, as if to say, “Follow me! It’s urgent!”

Eventually, Ted followed Spotty across the empty lot as Spotty stopped to race back and barked encouragingly. The little dog led the man to a deserted spot a half mile from the house. There Ted found his beloved Brownie alive, one of his legs crushed in a steel trap (圈套). Frightened, Ted now wished he had taken Spotty’s earlier appeals seriously.

Then Ted noticed something. Spotty had done something else besides leading Brownie’s human owner to his trapped friend. In a circle around the injured dog, Ted found some food remains of every meal. Brownie had been fed that week! Spotty had been visiting Brownie regularly, in the hope of keeping his friend alive. Spotty had actually stayed with Brownie to protect him from hunger and other dangers, and keep his spirits up.

Brownie’s leg was carefully treated and he soon got well again. For many years thereafter the two families watched the faithful friends chasing each other down that well-worn path between their houses.

小题1:At the very beginning, Ted paid little attention to Spotty because __________.

A.he was not free at the moment

B.he was sure Brownie would be OK

C.he didn’t like Spotty at all

D.his missing dog made him sad小题2:After Ted was brought where Brownie was trapped, he ___________.

A.managed to free his dog at once

B.was very thankful to Spotty

C.regretted not following Spotty earlier

D.was angry with the trap-maker小题3:The BEST title for this passage might be____________?

A.Dogs in Love

B.A Friend in Need

C.Human and dogs

D.Dogs Are Communicative小题4:We can infer from the passage that ___________.

A.humans and animals depend on each other for comfort

B.It’s not right to hunt for animals in any neighborhood

C.Ted has to take better care of his beloved dog later on

D.Brownie would have died without Spotty’s timely help

判断题