问题 问答题

已知箱中装有10件产品,其中一、二、三等品分别为7件,2件和1件,现从中取出两件产品,记试求:(Ⅰ)(X,Y)的概率分布;(Ⅱ)X与Y的相关系数ρ.

答案

参考答案:直接用定义计算.
(Ⅰ)由于[*],又P{X=1,Y=1}=0,根据联合概率分布与边缘分布关系,可求得(X,Y)的概率分布
[*]
(Ⅱ)由(X,Y)的概率分布,得
[*]
又P{XY=1}=P{X=1,Y=1}=0,P{XY=0

单项选择题
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Welcome to Language upon Thames. This brochure has been designed to give you an overview of our Language School and the courses we offer. If you have some additional questions please do not hesitate to contact us for more information.

At Language upon Thames,we feel it is important to be flexible,in order that students can decide what period of study suits them best.

Small Group General English Courses

These courses are aimed at students who wish to improve their speaking,listening,reading and writing skills and are offered at the following levels:

BEGINNERS

ELEMENTARY(初级)

PRE-1NTERMEDLATE

UPPER-INTERMEDLATE

Studying one of the above courses will enable you to use English more confidently and competently on a daily basis.

Try our free online test to see which level you are at—CLICK HERE.

Exam Courses

These courses ale aimed at students who wish to gain academic qualifications in English and are offered at the following levels:

University of Cambridge exams:

ADVANCED l — FCE (First certificate)

ADVANCED 2一CAE (Advanced)

ADVANCED 3一CPE (Proficiency)

Studying one of the above courses will enable you to continue your education or enter university in this country. (Students wishing to gain admission to a British university are normally required to have the Cambridge Proficiency Certificate.)

Speaking, Listening & Pronunciation

This course builds on communicative confidence and competence and is aimed at students who wish to develop the important skills of speaking and listening.

Emphasis is also placed on pronunciation,with activities designed to meet the needs of students of different nationalities,who need to focus on different areas.

CLICK HERE to register for a General English course.

Other Languages

At Language upon Thames we offer a wide range of cafeterias,restaurants,shops and bars. Most importantly,we have foreign language classes of French,Japanese,German,Spanish and Italian during the day,evening or on a one-to-one basis.

68. What does this passage mainly talk about?

A. English courses.

B. Ways to improve students’ English.

C. The best way to improve your skills.

D. The importance of English.

69. If you attend Exam Courses,you will     .

A. use English as fluently as a native speaker

B. deal with everyday English well

C. . have better pronunciation of English

D. be able to continue your education or enter university in this country

70. Judging from the description,we can tell that this passage must be taken from     .

A. a newspaper        B. a magazine

C. . the Internet            D. a guidebook

71. The following statements are true EXCEPT     .

A. Only Englishmen can attend the courses.

B. The courses are designed for learners of different levels.

C. . One can learn French even in the evening.

D. Language upon Thames is a school aimed to offer help with language learning.