# Homework help regression

Discussion in 'Homework Help' started by sunny1982, Mar 11, 2013.

1. ### sunny1982 Thread Starter Member

Dec 27, 2012
41
0
Hi folks
Yes its the annoying me again lol, I just can't stay away. Anyway another quick one for you clever folks.In this task I have tackled regression, in Task 2(a), I wondered if someone can check it and see if I have done this correctly.

"IF" I have done it correctly can someone be kind enough to show or advise me on how to do task 2(b).

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2. ### WBahn Moderator

Mar 31, 2012
23,571
7,214
What kind of regression are you supposed to be doing? Linear? Least squares?

You can do a quick sanity check by just using a couple of the points that don't seem like outliers and getting the slope and intercept (the temp at which the volume would be zero) and comparing that to your regression results.

3. ### sunny1982 Thread Starter Member

Dec 27, 2012
41
0
Hi its meant to be linear regression. Thats the bit I don't understand how to plot a graph the original task was done on excel spreadsheets.

4. ### sunny1982 Thread Starter Member

Dec 27, 2012
41
0
This is just great so I've got an assignment question that apart from the college teachers who set it know one else has a clue how to do it lol, I best go and suck up to my teacher and see if I can get him to help me. Thanks folks for looking anyway.

5. ### WBahn Moderator

Mar 31, 2012
23,571
7,214
I'm sorry that it has been 20 hours since I have been sitting at my computer with nothing better to do than help you with your homework. I must have had a mental hiccup that made me think that I had other things to do, such as plow the snow from the community roads, get blood work done, pick up my daughter from school, drive over a hundred miles to get certified copie of some legal documents and, oh, get some sleep. I completely forgot that I'm supposed to be sitting at my computer 24/7 waiting for your posts so that you don't have to deal with YOUR homework by yourself. Afterall, you are paying oh so much for this homework help service that it would be asking far too much to expect you not to get your knickers all twisted before you've even gone eight hours without a response.

Desides, my crystal ball needs new batteries so I wasn't able to read your mind to figure out what p, q, m, and c are in your "work".

So, yeah, perhaps you should go suck up to your teacher and see if you can get them to show you how to have Excel do even more of your thinking for you. That's probably your best bet since, by your own admission, asking you to plot two points on a piece of graph paper and draw a straight line that goes through them is too daunting a request.

As you say, obviously know one here has a clue how to do it. I just spend almost two minutes doing exactly what I suggested you do using your two extreme points and the line I drew only came was almost 2 degrees celsius away from the correct value for absolute zero. So what do I know?

6. ### #12 Expert

Nov 30, 2010
18,076
9,676
When I feel that pressured, I take a vacation from AAC for a few days, or even a few weeks,

7. ### sunny1982 Thread Starter Member

Dec 27, 2012
41
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I'm so sorry I never meant any offence by my last post I was just saying it in general, I was just thinking out loud No way did my comments refer to anybody on here once again sorry.

8. ### WBahn Moderator

Mar 31, 2012
23,571
7,214
Okay, so let's regroup and try again.

In the work that you posted there are four numbers off to the side labeled p. q. m, and c. What are those supposed to represent?

Since you are using linear regression, it has to be assumed that you are trying to model the data as a straight line of the form y=mx+b.

Since any two distinct points define a line, pick your most extreme points, the ones for T=90°C and the one for T=-50°C and find the equation of the line that goes through them. That's two equations and two unknowns (m and b). Is that something that you've been taught how to do?

Now, let's say that you find your values for m and b. What do you do with them?

Well, you are asked to do two things. Estimate what temperature is absolute zero and estimate the mass of the gas in the sample that the data was taken from.

For the first one, the key point is to consider what, theoretically, happens to the volume of an ideal gas at absolute zero?

For the second one, write the ideal gas law and match it up to the y=mx+b equation and see how you can solve for the mass of the gas.

Take your best shot at going from this and post your efforts. We can then see what your thinking seems to be and where you are going off on a tangent or misinterpreting something and guide you back toward the right path.

9. ### sunny1982 Thread Starter Member

Dec 27, 2012
41
0
m= (nƩxy)-(ƩxƩy) / (nƩx^2)-(Ʃx)^2

c = (Ʃx-Ʃm)*(Ʃx) / n

Thats what m and c mean in my work but I have been completed it heres the finished version m+c give me the value of zero.

Heres the completed version.
Thankyou, just wanted to say aswell I value your help I never forgot that before christmas you helped me complete that kirchoffs assignment which I passed and now if you gave me a circuit I'd probably solve it on my own lol.

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10. ### WBahn Moderator

Mar 31, 2012
23,571
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That doesn't tell me what they mean, just gives me an equation for how you calculated them.

The first is the simple least-squares linear regression equation for the slope of the best fit line. I have no idea what the second equation is and it is not dimensionally consistent (unless m happens to have the the same units as x). Also, what does Ʃm mean? Is it the m from the previous equation? If so, what is it summed over, since there's only one of them?