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sophie78
It's An Obsession
Member since 4/03 3421 total posts
Wedding Date:
9/18/2004 12:00 AM
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Long Shot but....does anyone know anything about...
How to test whether data is linear or not before using a Pearson's Correlation? Pearson's can only be used if it is linear. Do I make a scatterplot? So confused! Anyone have any ideas?
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Posted 6/8/05 1:03 PM 
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Janice
Don't call it a comeback
Member since 6/01 3270 total posts
Wedding Date:
6/1/2002 12:00 AM
Wed. Location:
Staten Island
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Re: Long Shot but....does anyone know anything about...
all greek to me
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Posted 6/8/05 1:09 PM
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sophie78
It's An Obsession
Member since 4/03 3421 total posts
Wedding Date:
9/18/2004 12:00 AM
Wed. Location:
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Re: Long Shot but....does anyone know anything about...
You teased me! I thought I had my answer!!!
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Posted 6/8/05 1:10 PM
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Re: Long Shot but....does anyone know anything about...
Posted by am470
How to test whether data is linear or not before using a Pearson's Correlation? Pearson's can only be used if it is linear. Do I make a scatterplot? So confused! Anyone have any ideas?
A scatter-what???? Not a clue
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Posted 6/8/05 1:11 PM
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Janice
Don't call it a comeback
Member since 6/01 3270 total posts
Wedding Date:
6/1/2002 12:00 AM
Wed. Location:
Staten Island
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Re: Long Shot but....does anyone know anything about...
sorry, I feel guilty when I read something and don't post. I hate it when posts don't get at least one answer. 
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Posted 6/8/05 1:11 PM
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RedHead
6 people and counting :*
Member since 10/03 18761 total posts
Wedding Date:
10/2/2004 12:00 AM
Wed. Location:
Fox Hollow :)
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Re: Long Shot but....does anyone know anything about...
Posted by am470
How to test whether data is linear or not before using a Pearson's Correlation? Pearson's can only be used if it is linear. Do I make a scatterplot? So confused! Anyone have any ideas?
in grad school i used only the Pearson...
never did scatterplots
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Posted 6/8/05 1:12 PM
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sophie78
It's An Obsession
Member since 4/03 3421 total posts
Wedding Date:
9/18/2004 12:00 AM
Wed. Location:
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Re: Long Shot but....does anyone know anything about...
Posted by RedHead
Posted by am470
How to test whether data is linear or not before using a Pearson's Correlation? Pearson's can only be used if it is linear. Do I make a scatterplot? So confused! Anyone have any ideas?
in grad school i used only the Pearson...
never did scatterplots
See you can't do Pearson's unless you test the data for linearity. But I totally forgot whether you eyeball it or whether there is a test for it. I hate dissertations!! And I hate professors who vacay all summer!!
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Posted 6/8/05 1:14 PM
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RedHead
6 people and counting :*
Member since 10/03 18761 total posts
Wedding Date:
10/2/2004 12:00 AM
Wed. Location:
Fox Hollow :)
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Re: Long Shot but....does anyone know anything about...
Posted by am470
Posted by RedHead
Posted by am470
How to test whether data is linear or not before using a Pearson's Correlation? Pearson's can only be used if it is linear. Do I make a scatterplot? So confused! Anyone have any ideas?
in grad school i used only the Pearson...
never did scatterplots
See you can't do Pearson's unless you test the data for linearity. But I totally forgot whether you eyeball it or whether there is a test for it. I hate dissertations!! And I hate professors who vacay all summer!!
 sorry...i didn't have to do that.
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Posted 6/8/05 1:15 PM
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cluelessbride
Bonjour!
Member since 8/02 4570 total posts
Wedding Date:
10/23/2004 11:00 AM
Wed. Location:
Danfords on the Sound
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Re: Long Shot but....does anyone know anything about...
Um, this is my really dumb answer but can you plot and if the slope is greater than 1 it's linear? Is it the plotting part that you need help with? 
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Posted 6/8/05 1:22 PM
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sophie78
It's An Obsession
Member since 4/03 3421 total posts
Wedding Date:
9/18/2004 12:00 AM
Wed. Location:
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Re: Long Shot but....does anyone know anything about...
Posted by cluelessbride
Um, this is my really dumb answer but can you plot and if the slope is greater than 1 it's linear? Is it the plotting part that you need help with?
No that's not it. But thanks anyway.
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Posted 6/8/05 1:33 PM
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Preshy7
I love being his wife
Member since 12/04 4958 total posts
Wedding Date:
4/22/2006 3:00 PM
Wed. Location:
Hamlet Willow Creek - PERFECTION
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Re: Long Shot but....does anyone know anything about...
this may or may not help ?
linear relationship
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Posted 6/8/05 2:11 PM
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nov04LIbride
Asshatery: Nature or nurture?
Member since 3/04 8138 total posts
Wedding Date:
11/6/2004 11:00 AM
Wed. Location:
Hard-boiled eggs also have hearts of gold.
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Re: Long Shot but....does anyone know anything about...
The scatterplot would show how strong the correlation is, and let you know whether run a Pearson's Correlation. If you can tell there is not a strong linear relationship by eyeballing it during the scatterplot, then it might not be worth it figuring out the Pearson's Correlation. We are using SPSS for our dissertations--do you use that? When you plus in the numbers it runs pretty much all of the tests, and shows scatterplots, etc.
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Posted 6/8/05 2:12 PM
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MCDO15
You got Served!
Member since 1/04 4741 total posts
Wedding Date:
3/13/2005 5:00 PM
Wed. Location:
Giorgio's at Fox Hill
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Re: Long Shot but....does anyone know anything about...
Posted by Preshy7
this may or may not help ?
linear relationship
lol, i just read the same thing...i think im a expert now...
i believe you want to do a scatterplot first to determine if its liner or not..then you can proceed
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Posted 6/8/05 2:15 PM
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dpli
"I'm Addicted"
Member since 1/04 2471 total posts
Wedding Date:
11/7/2004 3:30 PM
Wed. Location:
The Swan Club
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Re: Long Shot but....does anyone know anything about...
Most data is never completely linear but may have a linear relationship. From what I read about the Pearson's correlation, you are checking for linearity, so you should be able to do that with a scatterplot. I am not a behavioral scientist, though, so maybe it is used differently in your field.
Edited, b/c I think my first answer was wrong, sorry.
Message edited 6/8/2005 2:45:05 PM.
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Posted 6/8/05 2:42 PM
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sophie78
It's An Obsession
Member since 4/03 3421 total posts
Wedding Date:
9/18/2004 12:00 AM
Wed. Location:
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Re: Long Shot but....does anyone know anything about...
Posted by Preshy7
this may or may not help ?
linear relationship
Thanks but that is too simplistic for what I am doing.
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Posted 6/8/05 2:53 PM
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sophie78
It's An Obsession
Member since 4/03 3421 total posts
Wedding Date:
9/18/2004 12:00 AM
Wed. Location:
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Re: Long Shot but....does anyone know anything about...
Posted by nov04LIbride
The scatterplot would show how strong the correlation is, and let you know whether run a Pearson's Correlation. If you can tell there is not a strong linear relationship by eyeballing it during the scatterplot, then it might not be worth it figuring out the Pearson's Correlation. We are using SPSS for our dissertations--do you use that? When you plus in the numbers it runs pretty much all of the tests, and shows scatterplots, etc.
I am using SPSS. Most of my correlations are insignificant. The scatterplots seem to show no correlation but the data seems to be linear and not curvilienear. So eyeballing it is the answer! I also consulted my textbook which said that most social science data is linear. So I think my data is linear but not correlated for the most part!
Thanks. I hate dissertations.
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Posted 6/8/05 2:56 PM
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sophie78
It's An Obsession
Member since 4/03 3421 total posts
Wedding Date:
9/18/2004 12:00 AM
Wed. Location:
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Re: Long Shot but....does anyone know anything about...
I am using SPSS. Most of my correlations are insignificant. The scatterplots seem to show no correlation but the data seems to be linear and not curvilienear. So eyeballing it is the answer! I also consulted my textbook which said that most social science data is linear. So I think my data is linear but not correlated for the most part! So I can use the Pearson's!
Thanks. I hate dissertations.
Message edited 6/8/2005 2:57:04 PM.
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Posted 6/8/05 2:56 PM
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dpli
"I'm Addicted"
Member since 1/04 2471 total posts
Wedding Date:
11/7/2004 3:30 PM
Wed. Location:
The Swan Club
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Re: Long Shot but....does anyone know anything about...
My other thought is: can you use the variance values of your data to determine the linearity? Like if the variance is over a certain # you cannot consider it linear? If so, you could do a spreadsheet to calculate the variance values if your data is already entered as if you were doing a scatterplot pretty easily.
ETA: Never mind - it looks like you figured it out 
Message edited 6/8/2005 3:02:37 PM.
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Posted 6/8/05 2:58 PM
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sophie78
It's An Obsession
Member since 4/03 3421 total posts
Wedding Date:
9/18/2004 12:00 AM
Wed. Location:
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Re: Long Shot but....does anyone know anything about...
dpli-I don't think it works that way. But I could be wrong. The Levene's test for equality of variances when I did my t-tests all came up non significant which is good.
Message edited 6/8/2005 3:13:40 PM.
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Posted 6/8/05 3:11 PM
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sjm71505
Board Enthusiast
Member since 5/04 245 total posts
Wedding Date:
7/15/2005 6:00 PM
Wed. Location:
Carlyle on the Green
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Re: Long Shot but....does anyone know anything about...
I am getting my doctorate in psych too...so let's see if all those classes in stat paid off!
I would say that the correlation is the "test" for linearity. If the correlation is signficant that means there is a significant relationship between the variables. If there is a curvilinear relationship, the correlation may come out to be insignficant because a product-moment corelation coefficient is sensitive to a LINEAR relationship between two variables . However, just because the P-Moment Coeff. is insignificant does not mean there is NO relationship between the variables. If you do a scatter plot, the curvilinear relationship may become more evident, which would then make your insignficant finding significant (in a nonstatistical sense). there may be some other test or analyses that can be done to see if the curvilinear relationship is signficant....but I don't know what it is off hand.
HTH
Now, if only I could get motivated to work on my dissertation 
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Posted 6/8/05 8:05 PM
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sophie78
It's An Obsession
Member since 4/03 3421 total posts
Wedding Date:
9/18/2004 12:00 AM
Wed. Location:
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Re: Long Shot but....does anyone know anything about...
Posted by sjm71505
I am getting my doctorate in psych too...so let's see if all those classes in stat paid off!
I would say that the correlation is the "test" for linearity. If the correlation is signficant that means there is a significant relationship between the variables. If there is a curvilinear relationship, the correlation may come out to be insignficant because a product-moment corelation coefficient is sensitive to a LINEAR relationship between two variables . However, just because the P-Moment Coeff. is insignificant does not mean there is NO relationship between the variables. If you do a scatter plot, the curvilinear relationship may become more evident, which would then make your insignficant finding significant (in a nonstatistical sense). there may be some other test or analyses that can be done to see if the curvilinear relationship is signficant....but I don't know what it is off hand.
HTH
Now, if only I could get motivated to work on my dissertation
I know that correlations do not equal linearity. They are too different things. I definitely think checking out the scatter plot is the way to go.
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Posted 6/8/05 9:13 PM
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