问题 问答题

试结合可行集的图形推导马科维茨有效边界。

答案

参考答案:有效集是指同时满足以下条件的证券组合:①对于每一风险的水平,提供最大的期望收益率;②在每一期望收益率水平下,提供最小的风险。
如图7-4所示,在所有的证券组合中,E点的风险是最小的,因为过E点作横轴的垂线,可行集中没有哪一点在这条线的左边;H点是风险最大的,因为过H点作横轴的垂线,可行集中没有哪一点在这条线的右边。所以E点到H点界定了各种证券组合所能提供的风险水平的范围。在这个范围内,任作一条横轴的垂线,我们可以看到在给定的风险水平上,期望收益率最大的组合总是位于从E点到日点的曲险段上。因此满足第一个条件的组合位于可行集中从E点到H点的左上方边界上。
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同样道理,我们可以确定满足第二个条件的组合。在所有的证券组合中,G点的期望收益率是最小的,因为过G点作纵轴的垂线,可行集中没有哪一点在这条线的下方;H点的期望收益率是最大的,因为过H点纵轴的垂线,可行集中没有哪一点在这条线的上方。所以G点到H点界定了各种证券组合所能提供的期望收益率的范围。在这个范围内,任作一条纵轴的垂线,我们可以看到在给定的期望收益率水平下,风险最小的组合总是位于从G点到H点的左边界上。
由于有效集必须同时满足上述两个条件,所以只有EH曲线段和GH曲线段的交集,即EH曲线段才能同时满足两个条件,即可行集中从E点到H点的证券组合才构成有效组合。由所有有效组合组成的曲线段EH,就是马科维茨有效边界。

阅读理解
阅读理解。
     What makes a house a home?
     Not size,of course.I've been in some of the grandest houses in America,and it's clear that no one
lives there.Earlier this year,I had dinner in a mud hut in Ethiopia,where we sat on chairs next to the
hostess' bed-a home that had more warmth than any house I've been in since.
     Now John Edwards is exploring what makes a house a home in his justreleased(发行)Home.The
Blueprints of Our Lives.There Edwards writes,"This isn't a book about houses;it's a book about
homes.About the values they rest on,the dreams they are filled with,and the people they have shaped
."Edwards writes,"The houses and circumstances are different,but much of what you find inside will
be familiar."
      Whether you're sitting in an airport right now,waiting to fly to your childhood home for Thanksgiving,
or in your own home waiting for the relatives to arrive,you know what he's talking about.
      We've lived in our townhouse for 21 years.It's home now.The loose windows that shake in the wind.
The fireplace so shallow it holds only one log.The kitchen window that offers a view of the world passing
by.It's where friends sit on the kitchen counter drinking wine while dinner is being fixed.I lived there for
only 18 years,but it will always be my true home.Even the lamp in the west living room window,which I
could see far down the road when driving home late at night,still shines.
      While all this talk about childhood memories can be warm and comforting,home is whom you're with,
not where you are.As Edwards writes,"Home is family.Home is safety.Home is faith."
     Happy homecoming.
1.According to the author,what makes a house a home?
A.All the belongings in the house.
B.Feelings of warmth and comfort.
C.The houses and circumstances.
D.Drinking with friends on the kitchen counter.
2.About the book Home: The Blueprints of Our Lives,we know that ________.
A.it was the description of Edwards' houses
B.it is mainly about houses
C.it helps us understand the concept(概念)of home
D.it was written by the author of the text
3.What did the author mean when he mentioned the loose windows and the shallow fireplace?
A.His house was too old to live in.
B.He missed the feeling of home.
C.He hated living there.
D.He missed his old friends too much.
4.It can be inferred according to the text that ________.
A.the author's family was very rich
B.every happy home is the same
C.the author has been living an unhappy life
D.the author and Edwards hold similar ideas
单项选择题