1 Topic by johnniks (edited by johnniks 2013-08-12 16:11:03)

Topic: Linear regression, how to find a and b? Plz help

Hello,

Okay so when I type in the following information:
X,Y
2007,195
2008,190
2009,161
2010,110
2011,107
2012,82

It's something about how many people dies each year in traffic (doesn't really matter).

Then it says: f(x)=-24.7143*x+4.9804E+04; R2=0.9447

I realize that -24.7143 is my a but how do I find my b?

Any help would be really appreciated as I might need this in 2 days for my exam.

Re: Linear regression, how to find a and b? Plz help

Hi there,

by "a" and "b", I'm guessing you mean the following linear equation formulation:
y = ax + b

"b" would simply be the other number in the equation you got, in this case:
b = 4.9804E+04

3 Reply by johnniks (edited by johnniks 2013-08-12 17:53:23)

Re: Linear regression, how to find a and b? Plz help

Thanks for replying, but are you sure? well, yes it looks correct as to what you're saying but My Answer Book on this one says b is supposed to be 202.62, i don't quite see how it becomes 202.62 is there something i'm not seeing or did i do something wrong?

I'm not all that good at using my TI-89 so i'd rather try to figure it out Graph (it seems way easier), my guide on TI-89 says something about "m*x+b" and (a = stat.m; b = stat.b) which I'm not getting at all... maybe it makes sense to someone else here?

Re: Linear regression, how to find a and b? Plz help

I think the difference is that you are supposed to use the following coordinates:

0,195
1,190
2,161
3,110
4,107
5,82

However I would think that your original way of doing it is just as correct.

Re: Linear regression, how to find a and b? Plz help

ah, now it gives me the same results as my Answer Book does, thanks a lot! <3

Re: Linear regression, how to find a and b? Plz help

Good eyes, Ivan wink

I had a fleeting thought about that when I first replied, but it seems I just let it go... wink