[R] [r] ANCOVA method

[Bert Gunter]

Francesco:

1. You need to seek local statistical help.

2. The answer to your question is: it depends in how you define
"influence significantly." If you define it as "the interaction term
is significant" then, by definition the answer is yes. If you want to
understand what is going on and make meaningful scientific statements,
then the answer is no. At the least, you need to plot your data
informatively. To determine what this means, see (1) above.

Cheers,
Bert

On Fri, Dec 3, 2010 at 8:13 AM, Francesco Nutini
<nutini.francesco at gmail.com> wrote:
>
>  Dear [R] Users,
> I have implemented a linear model with this syntax:
>
> model<-  lm  (var_dependent ~ var_indipendent + factor +  var_indipendent : factor, dataframe)
> anova (model)
> Response: var_dependent
>                                  Df  Sum Sq  Mean Sq  F value    Pr(>F)
>        var_indipendent           1   20.5522 20.5522  87.8701    1.167e-14 ***
>        factor                    1   0.1060  0.1060   0.4530     0.50277
>        var_indipendent:factor    1   1.3861  1.3861   5.9261     0.01706 *
>        Residuals                 83  19.4132 0.2339
>        ---
>        Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
> If I read the line "var_indipendent:factor" can I understand if the factor influence significatvly the regression between dependent-indipendent variable?
>
> Thanks a lot!
> Francesco Nutini
>
> P.S. numbers have no significance, it's just an example
>
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>
>
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-- 
Bert Gunter
Genentech Nonclinical Biostatistics