Regression Final

[Bühlmann]

Word on the street was that today's exam was kinda hard. Wonder what that means for the Time Series final?

[Selena]

did you save your answers?

[Selena]

Does anyone know the formula for elastisities (sp?) ? I thought it was B (Beta), the slope coefficient?

[jingle47]

I saved my answers and am ready for a pak....

[Bühlmann]

did you save your answers?

I'm sitting for Time Series. A co-worker took Regression.

[bucks22]

I think there were a few typos on the exam as well. There is nothing more frustrating than that when taking a test. Did anyone else notice this?

[joeorez]

Elasticity = (Beta Hat j) * (X Bar j / Y Bar).

Anyone get the wrong answer for RSS in question 6, and therefore unable to continue with 7 through 13? Not a good start.

[jingle47]

How about the ARCH question? I totally skipped the reading and so I guessed A for #49

[Selena]

Elasticity = (Beta Hat j) * (X Bar j / Y Bar).

Anyone get the wrong answer for RSS in question 6, and therefore unable to continue with 7 through 13? Not a good start.

I multiplied my answer by 100 to get their answer and continued.

[NewTubaBoy]

People thought it was hard... crap... I guess I should go and do some studying for my time series final. The LAST thing I want to do is fail this exam and have to retake the darn final.

[Selena]

I saved my answers and am ready for a pak....

I will send you my answers if you send me yours. PM me

[NewTubaBoy]

typos aside, for those who actually took it, do you also agree that it was more difficult than either the practice problems or than expected?

[joeorez]

Which problems do you think had typos?

[pi_rsquare]

I multiplied my answer by 100 to get their answer and continued.

Yep, I did exactly the same thing :)

[red]

Can anyone confirm that it was harder than the sample problems that were posted? I took Regression in July and the test was the same as the samples. I am getting ready to take Time Series on Friday and want to know if I should be putting in a lot more time.

Thanks.

[jingle47]

I would put a little more time into it....

[Patriots' Fan]

Elasticity = (Beta Hat j) * (X Bar j / Y Bar).

Anyone get the wrong answer for RSS in question 6, and therefore unable to continue with 7 through 13? Not a good start.

Did anyone get something like 0.36 for the variance? It was from there on I wasn't sure if I was systematically wrong because I wasn't sure about what I got for the variance... does 0.36 sound familiar to anyone?

[Selena]

Did anyone get something like 0.36 for the variance? It was from there on I wasn't sure if I was systematically wrong because I wasn't sure about what I got for the variance... does 0.36 sound familiar to anyone?

Yes I got 0.0036, that answer was not on their choice list, so I multiplied it by 100 and chose 0.36 as an answer. I figured that 0.36 is 0.0036 x 100%, since we were dealing with %.

[Patriots' Fan]

Yes I got 0.0036, that answer was not on their choice list, so I multiplied it by 100 and chose 0.36 as an answer. I figured that 0.36 is 0.0036 x 100%, since we were dealing with %.

And then the answer for one of the questions, maybe RSS, was like +1?

[Selena]

And then the answer for one of the questions, maybe RSS, was like +1?

I do not think so

[Patriots' Fan]

I do not think so

Or was it TSS, or R^2? what did you get for them?

[Selena]

Or was it TSS, or R^2? what did you get for them?

I do not remember now. TSS, ESS, RSS were all <1, but something else was +1...do not remember what it was thou.

[joeorez]

I am curious which questions people think had typos.

[jingle47]

did anyone else notice that two of the choices for the F-test were negative?
That narrows things down a bit.

Also:on # 17, Choices A,B,and C gave that alpha would go up, down, or stay the same.....So you know it has to be 1 of those 3 and therefore can eliminate choice D or E no matter what the question asked.

[cincinnatikid]

Also:on # 17, Choices A,B,and C gave that alpha would go up, down, or stay the same.....So you know it has to be 1 of those 3 and therefore can eliminate choice D or E no matter what the question asked.

Seems logical, and I struggled but I actually think I chose either D or E on that one....

IIRC, Choices A, B, and C had to do with the change in alpha if the X's were increased by 1. If you increase X by 1, the change in alpha depends on whether beta is positive or negative, so I threw out all of A, B, and C. Adding 1 to the Y's appears to ALWAYS (perhaps that word should have been added to the choices) increase alpha by 1, so I picked whichever choice that was.

[Patriots' Fan]

Wasn't the beta negative?

[cincinnatikid]

Wasn't the beta negative?

I didn't get the impression it was relating to any particular alpha or beta, but that the question was about the relationship in more of a general sense.

[Chubbs]

I am curious which questions people think had typos.

Question 21 had a typo. In the question they tell you that B (hat) is .500 and then ask you to talk about the change in B hat. But all the answers relate to B hat being greater to or less than .600

This typo wasn't too hard to figure out, I think they meant to use .500 in all the answers, but reading the question the way it was written, you can't solve it.

Also, in question 28 they ask for the elasticity of the variable X2.

Partial deriv of Y with respect to X2 is .4
X2 bar is -.2
Y bar is .08

.4 * -.2/.08 is -1 I assumed they made a decimal place error and chose -.1

[cincinnatikid]

Question 21 had a typo. In the question they tell you that B (hat) is .500 and then ask you to talk about the change in B hat. But all the answers relate to B hat being greater to or less than .600

This typo wasn't too hard to figure out, I think they meant to use .500 in all the answers, but reading the question the way it was written, you can't solve it.

Also, in question 28 they ask for the elasticity of the variable X2.

Partial deriv of Y with respect to X2 is .4
X2 bar is -.2
Y bar is .08

.4 * -.2/.08 is -1 I assumed they made a decimal place error and chose -.1

Agree on both of these.

[Patriots' Fan]

For one of the answers I got something like 0.25 and it only has the choice 0.20. I was so sure about my answer I just chose 0.20 and moved on.

Does anyone remember this problem?

[Chubbs]

Did anyone get something like 0.36 for the variance? It was from there on I wasn't sure if I was systematically wrong because I wasn't sure about what I got for the variance... does 0.36 sound familiar to anyone?

In question 1.8, they ask for the varience of the regression. Is that what you are talking about. Because I got .0039% and didn't need to multiply anything.

In question 1.9 they ask for the variance of the B estimator. This is the varience of the regression divided by the sum of the (X-Xbar).

This yields a nice clean 3.9% The rub is, you have answers of .39% and 3.89%

I chose the .39% because I was assuming a decimal error, but I didn't multiply by 100, it was only 10. and i was using 39 not 36, so I am little confused as to what you may be talking about

[Patriots' Fan]

In question 1.8, they ask for the varience of the regression. Is that what you are talking about. Because I got .0039% and didn't need to multiply anything.

In question 1.9 they ask for the variance of the B estimator. This is the varience of the regression divided by the sum of the (X-Xbar).

This yields a nice clean 3.9% The rub is, you have answers of .39% and 3.89%

I chose the .39% because I was assuming a decimal error, but I didn't multiply by 100, it was only 10. and i was using 39 not 36, so I am little confused as to what you may be talking about


How did you get .0039% for the variance of the regression?

Yeah, I got 3.89% too for the variance of beta and picked the 3.9% answer. But I was more thinking of the variance of the regression problem.

[Chubbs]

How did you get .0039% for the variance of the regression?

Yeah, I got 3.89% too for the variance of beta and picked the 3.9% answer. But I was more thinking of the variance of the regression problem.

The variance of the regression can be found by dividing the ESS by the degrees of freemdom.


.0117/3=.0039

[Selena]

Also, in question 28 they ask for the elasticity of the variable X2.

Partial deriv of Y with respect to X2 is .4
X2 bar is -.2
Y bar is .08

.4 * -.2/.08 is -1 I assumed they made a decimal place error and chose -.1

Did either of you send an email to NEAS mentioning these errors? If not I will send one.

[jingle47]

I think you should send an email whether they did or not.