Bookmark and Share

Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down on April 23, and its replacement, statalist.org is already up and running.


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: st: difference in lfit slop


From   Austin Nichols <austinnichols@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: difference in lfit slop
Date   Tue, 4 Oct 2011 10:06:40 -0400

Lars Folkestad <lfolkestad@health.sdu.dk>:

regress metode1 age
est sto m1
regress metode2 age
est sto m2
suest m1 m2
test [m1_mean]_b[age]=[m2_mean]_b[age]

On Tue, Oct 4, 2011 at 9:30 AM, Lars Folkestad <lfolkestad@health.sdu.dk> wrote:
> dear list
> i am doing a twoway scatte:
>
> twoway (scatter methode1 age) (scatter metode2 age) (lfit methode1 age) (lfit methode2 age)
>
> this gives two different lfit slopes, one for metode1 and one for metode2 by age. i would like investigate if this slope is different. i understand that i could investigate the coef from the two liniar regressions:
>
> regress metode1 age
> regress metode2 age
>
> using the methode described by clogg et al:
>
>  z= (b1-b2)/squ(SEb1e2-SEb2e2)
>
> where b1 is the estimated slope1 (metode1) and SEb1 is the standard error for metode1.
>
> my questions:
> how do i do this in stata?
> is the slope1 (b1) the same as _cons dfrom the metode1 regression model
> in the litterature, i've seen that z-values above 2 in large samples are signifikant. my sample is petit.
> so what z value is enough to discard rhe null hypothisis= there is no difference between the groups.
>
> thank you for your answer
>

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/


© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   Site index