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The monthly returns of two portfolios are to be compared. The…

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The monthly returns of two...
The monthly returns of two portfolios are to be compared. The monthly returns are analyzed for each of 13 months, with the months being chosen at random and independently for the two portfolios. The following statistics for monthly returns are reported for portfolio 1 and portfolio 2 :

Portfolio 1Portfolio 2
x1 = .12 x2 = .13
s21 = .0049s22 = .0025

(The first row gives the sample means, and the second row gives the sample variances.)
Assume that the monthly returns of the two portfolios are each normally distributed. Construct a 90% confidence interval for o12/o22, the ratio of the variances of the monthly returns for these two portfolios. Then complete the table below.

Carry your intermediate computations to at least three decimal places. Write your final responses to at least two decimal places.

What is the lower limit of the 90% confidence interval?
What is the upper limit of the 90% confidence interval?

Let me know if you need a screen shot of the question - the upper and lower power numbers don't translate well in plain text like this so it may be confusing.

fyi there is a time limit on this - if you can't answer within the next five minutes please let me know and I can move on to another question. thx!
Submitted: 8 years ago.Category: Math Homework
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7/3/2010
Math Tutor or Teacher: rajeevanpillai, Master's Degree replied 8 years ago
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Customer reply replied 8 years ago
Lower confidence limit is incorrect....
Math Tutor or Teacher: rajeevanpillai, Master's Degree replied 8 years ago
Which lower limit ? The first one or second.
It should be correct.
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Math Tutor or Teacher: rajeevanpillai, Master's Degree replied 8 years ago
It is correct.
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Customer reply replied 8 years ago

You tell me. I only need one lower limit and one upper limit. You gave me two of each.

I need to know:

 

What is the lower limit of the 90% confidence interval?

What is the upper limit of the 90% confidence interval?

Math Tutor or Teacher: rajeevanpillai, Master's Degree replied 8 years ago
You take the one for σ1^2 / σ2^2 .
The other one is for σ2^2 / σ1^2 .
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Customer reply replied 8 years ago
My key says that upper of 3.6472 is correct but the lower of 1.0533 is not correct.
Math Tutor or Teacher: rajeevanpillai, Master's Degree replied 8 years ago


What is the lower limit for your key?
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Customer reply replied 8 years ago
it doesn't tell me, I have to tell it. I can quit the question and then it will tell me. Want me to do that and then we can work on another question? I won't get credit for this one if I don't answer it correctly.
Math Tutor or Teacher: rajeevanpillai, Master's Degree replied 8 years ago
My answer is correct . I have verified it. Your key seems to be wrong.
If you have Ms excel use the formuls = FINV(0.95,29,29) to find the F-value. Then multiply it with s2^2/s1^2.

This is the method

For upperlimit use =FINV(0.05,29,29)
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Customer reply replied 8 years ago

It says the answers are:

lower limit: .73

upper limit: 5.27

 

Let's try a diff question:

The lifetime of a certain brand of electric light bulb is known to have a standard deviation of 50 hours. Suppose that a random sample of 60 bulbs of this brand has a mean lifetime of 477 hours. Find a 90% confidence interval for the true mean lifetime of all lightbulbs of this brand. Carry computations to at least three decimal places. Round answers to one decimal place.

 

What is the lower limit of the 90% confidence interval?

What is the upper limit of the 90% confidence interval?

 

Math Tutor or Teacher: rajeevanpillai, Master's Degree replied 8 years ago
click here

rajeevanpillai
rajeevanpillai, Master's Degree
Category: Math Homework
Satisfied Customers: 741
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Customer reply replied 8 years ago
Excellent - thank you!
Math Tutor or Teacher: rajeevanpillai, Master's Degree replied 8 years ago
Thanks.
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