# st: loneway - comparing SD's

 From Rebecca Thornton <[email protected]> To [email protected] Subject st: loneway - comparing SD's Date Mon, 10 Nov 2003 18:49:05 -0500 (EST)

```I'm trying to compare the estimated SD of "between" and "within" variances
for two groups, a treatment group and a comparison group.  Is there a
suggested way to recover the standard errors in order to test the
hypothesis that (estimated SD between effect Treatment group) = (estimated
SD between effect Comparison group) ?

For example:
The output from loneway for the treatment group is:

loneway score00nm schid if std==6 & teso==0 & male==0 & treat==1

One-way Analysis of Variance for score00nm:

Number of obs =       345
R-squared =    0.5995

Source                SS         df      MS            F     Prob > F
-------------------------------------------------------------------------
Between schid          160.00569     30    5.3335229     15.67     0.0000
Within schid           106.89158    314    .34041906
-------------------------------------------------------------------------
Total                  266.89727    344    .77586416

Intraclass       Asy.
correlation      S.E.       [95% Conf. Interval]
------------------------------------------------
0.57069     0.07739       0.41900     0.72238

Estimated SD of schid effect            .6727015
Estimated SD within schid               .5834544
Est. reliability of a schid mean         0.93617
(evaluated at n=11.03)

and for the comparison group is :

loneway score00nm schid if std==6 & teso==0 & male==0 & treat==0

One-way Analysis of Variance for score00nm:

Number of obs =       404
R-squared =    0.5171

Source                SS         df      MS            F     Prob > F
-------------------------------------------------------------------------
Between schid          169.09683     33    5.1241465     12.01     0.0000
Within schid           157.89682    370    .42674816
-------------------------------------------------------------------------
Total                  326.99365    403    .81139864

Intraclass       Asy.
correlation      S.E.       [95% Conf. Interval]
------------------------------------------------
0.48329     0.07764       0.33111     0.63546

Estimated SD of schid effect            .6317745
Estimated SD within schid               .6532596
Est. reliability of a schid mean         0.91672
(evaluated at n=11.77)

I want to test that hypothesis that 0.6727 = 0.63177

but don't know how to recover the standard errors.

Thanks,

Rebecca
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