7. For a random variable X, .Find E(X²) .

6. For a random variable X, Var(X) =11 and E(X2) = 36. Find the mean of X .

5.Suppose that a random variable X is such that E(X) = 5.7 and Var(X) = 2.5. Suppose further that Y is a random variable such that Y = 4 2X. Find E(Y) and Var(Y) .

4. For this probability distribution given in the following table:

a. For this probability distribution,find the mode of X.

b. For this probability distribution ,find the median of X.

c. For this probability distribution,find the expected value E(X) .

d. For this probability distribution find the variance Var(X).

e. For this probability distribution find the Sd(X).

3.Suppose that the random variable X has the probability distribution given in the following table:

Then find the .

2.Which of the following tables could represent a probability distribution of a discrete random variable?

1. Consider the following table:

For the table to represent a probability function ,Find the value of k .

第二节：书面表达(25分)

最近，你看到某英文报纸正在征集主题为“如何才能受人欢迎”的短文，对此你很兴趣。请你根据以下提示谈谈自己的想法，给该报社投稿。

要点提示：

　　　 1、衣着干净、整齐，保持微笑；　

　　　 2、诚实，乐于助人；

　　　 3、懂得与人合作；　　　　　　　

　　　 4、其他。

注意：1词数不少于100；2文章的标题和开头已为你写好(不计入总数)；③可根据内容要点适当增加细节，以使行文连贯。

How to be popular

　　　 Most people would like to be popular with others, but what is the secret to achieve popularity?

　　　 In fact, it is very simple…

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

第一节：短文改错(共10小题；每小题1分，满分10分)

在答题卡上改正所给短文中的错误。对标有题号的每一行做出判断：如有错误(每行只有一个错误)，则按下列情况改正：该行多一个词：把多余的词用斜线(＼)划掉，在该行右边横线上写出该词，并也用斜线划掉。该行缺一个词：在缺词处加一个漏字符号(∧)，在该行右边横线上写出该加的词。该行错一个词：在错的词下划一横线，在该行右边横线上写出改正后的词。

　　　 Dan was the doorman of a club in the big city. Every　　　　　　　　 76. 　　　　　　

day, thousands of people passed his door, but a lot of 　　　　　　　　　　　　　　 77. 　　　　　　

them stopped and asking him, "What's the time, please?" 　　　　　　　　 78. 　　　　　　

　　　 After few months, Dan said to himself, "I'm not　　　　　　　　　　　 79. 　　　　　　

going to answer all those stupid people no more. I'm　　　　　　　　　　　　 80. 　　　　　　　

going to buy a big clock and put them upon the wall 　　　　　　　　　　　 81. 　　　　　　

here." Then he does so. 　　　　　　　　　　　　　　　　　　　　　 　　　　　　　　　　　　　　 82. 　　　　　　

　　　 "Now people are going to stop to ask me the time," 　　　　　　　　 83. 　　　　　　

he thought happy. But after that, a lot of people stopped, 　　　　　　　　 84. 　　　　　　

looked at the clock and then asked Dan, "Is that clock all right?" 　　　 85.