View Question
Q: relationship between the intercept and co-efficient of variation ( Answered ,   0 Comments )
 Question
 Subject: relationship between the intercept and co-efficient of variation Category: Science > Math Asked by: blurb-ga List Price: \$10.00 Posted: 20 Apr 2003 05:48 PDT Expires: 20 May 2003 05:48 PDT Question ID: 192929
 ```Is there a direct relationship between the coefficient of variation for a variable and the t statistic for the intercept(for a regression that includes several explanatory variables modelling the original variable)?``` Request for Question Clarification by jeremymiles-ga on 21 Apr 2003 01:49 PDT ```What might cause the coefficient of variation to change? Would it be random sampling variation, or would it be that you are carrying out a transformation of some sort on the variable? jeremymiles-ga``` Clarification of Question by blurb-ga on 21 Apr 2003 04:00 PDT ```Jeremy I was thinking more of a series of variables, say product sales for five different brands of coffee. I'm wondering if its valid to make an inference about a more stable 'base' for the brands that have a lower cv? With the data I have there seems to be a connection, and it seems intuitive that it should be so, but I can't prove that this is a wider, verifiable phenomenon. Thanks Robert``` Request for Question Clarification by jeremymiles-ga on 22 Apr 2003 03:04 PDT ```Hello Blurb, Can you explain a little more about your analysis. The intercept is a curious thing - it is affected by the scale of your measure(s), the means, and the independent variables. Sometimes it is meaningless, other times useful. jeremymiles-ga``` Clarification of Question by blurb-ga on 27 Apr 2003 13:28 PDT ```jeremymiles after some consideration i think i may have asked a non-question. i think i'd like to clarify my question down to this: what interpretation should i give to the t statistic of the intercept? is it actually saying something about the stability of the mean? if you don't accept this as a clarification then let me know and i'll repost. thanks blurb```
 ```The t-statistic isn't telling you very much about the stability of the mean - rather it is telling you about the likely difference between the intercept and zero. However, this doesn't necesarily make any sense, for two reasons: 1. The intercept doesn't always make sense - the intercept is the estimate of the value of the outcome variable, when all predictors are equal to zero. If it is not possible for some, or all, predictors to be zero, it's not worth considering the intercept out of context. 2. A transformation of the predictors can change the intercept - thsi might happen if you change the reference category of a nominal variable, or if you use a different zero point for your measure (many measures have arbitrary zero points - e.g. earnings could use zero as the zero, or could use the minimum wage, which is effectively zero). If you are interested in the stability of the mean, I would consider looking at the standard error. jeremymiles-ga``` Clarification of Answer by jeremymiles-ga on 29 Apr 2003 05:48 PDT ```I meant to add: If you require more information, please don't hesitate to request clarification. Issues in regression can become complex quite fast. jeremymiles-ga```