# Linear regression

Six Sigma – iSixSigma Forums Old Forums General Linear regression

This topic contains 5 replies, has 5 voices, and was last updated by  Darth 13 years, 9 months ago.

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• #41895

Jeff
Participant

I was analyzing a linear regression with fish mass on the x-axis and nutrient excretion rate on the y-axis. I was wanting to determine the p-value of this data to see if there is a significant difference between the excretion rate of small fish versus large fish (indicated by the slope of the line). Could someone help me with how to go about this.Thanks.
Jeff

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#131928

Darth
Participant

You seem to be asking two questions……Is there a relationship between fish mass and how much fish poop is produced.  Regression is used for that.  Then you ask is there a difference between the poop rate of small versus large fish.  You would use Hypothesis Testing, specificially a two-sample t or some equivalent to answer that.  If you did a scatterplot of the data (fish mass vs poop rate) but distinguished small vs large, you could get a visual picture based on the plot.  The best way to do all of this is with some statistical software, particularly Minitab.

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#131932

Jered Horn
Participant

A scatterplot with fist poop…sounds fun.
Isn’t it obvious that the big guys would put out more???

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#131933

AT
Participant

The options that you have is to first of all establish that there is a correlation between the excretion rate and the fish mass. You can do it by finding the coefficient of correlation between the two. if r is significant then you do a hyp test. You can use excel for these tests. These question has been answered several times on this forum.
https://www.isixsigma.com/forum/showmessage.asp?messageID=83883
https://www.isixsigma.com/forum/showmessage.asp?messageID=82809
https://www.isixsigma.com/forum/showmessage.asp?messageID=82234

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#131934

Patt
Participant

I agree with Jeff..
Maybe someone is having fun with this discussion.

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#131935

Darth
Participant

Yes, the bigger they are the greater the volume of poop.  Look at Stan and Carnell for affirmation of that relationship.  But, what is the relationship?  Is it linear?  Twice as big gives you twice as much?  Or is there some other relationship?  In my home fishtank this would be useful to predict so that I know how many catfish to put in to keep the tank clean….knowing the amount of FP they can consume.

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