# Re: st: Re: XTMixed / Repeated Measures

 From David Airey To statalist@hsphsun2.harvard.edu Subject Re: st: Re: XTMixed / Repeated Measures Date Wed, 31 Dec 2008 09:44:47 -0600

```use http://www.ats.ucla.edu/stat/stata/examples/kirk/rb4, clear
anova y a s, repeated(a)
test _coef[a[3]] = _coef[a[4]]
anova, regress // note a[4] was dropped
xi: xtmixed y i.a || s: // note a[1] was dropped
test _Ia_3 = _Ia_4
display r(chi2)/r(df) // scale to show F the same, but here df 1

```
...shows the same results, yes, and wrt your question, the coefficients shown are relative to the dropped group, in this model. You can also change which group gets dropped.
```

On Dec 31, 2008, at 8:37 AM, Paul Bransom wrote:

```
```Sorry - forgot the subject on my earlier posting

Hello,
```
I am trying to teach myself how to use xtmixed for repeated measures anova. Using anova:
```
anova m method id,repeated(method)
I have a significant effect of method and I can compare the methods:
```
test _coef[method[1]] = _coef[method[2]] ( 1) method[1] - method[2] = 0
```      F(  1,    27) =   58.27
Prob > F =    0.0000

However when I use xtmixed
xi:xtmixed m i.method || id:

-----

------------------------------------------------------------------------------
```
m | Coef. Std. Err. z P>|z| [95% Conf. Interval] ------------- +----------------------------------------------------------
```-------------+------
```
_Imethod_2 | -12.6 1.650589 -7.63 0.000 -15.8351 -9.364905 _Imethod_3 | -15.1 1.650589 -9.15 0.000 -18.3351 -11.8649 _Imethod_4 | -11.1 1.650589 -6.72 0.000 -14.3351 -7.864905 _cons | 38.6 2.253023 17.13 0.000 34.18416 43.01584
```
I can again compare all the methods:

. test _Imethod_2  = _Imethod_3

```
with the exception of method 1 as _Imethod_ is the "reference" in the equation. My question is - how can I compare the effect of method 1 to the other methods or is the fact that these coefficients have a significant p value sufficient (or am I missing something that is so obvious)?
```
I am using Stata 10.
Thanks,
Paul

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```
```
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```