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Re: st: r(198) error using lrtest to test for heteroskedasticity.


From   Sean Lim <seanlim174@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: r(198) error using lrtest to test for heteroskedasticity.
Date   Sat, 7 Jul 2012 00:07:22 +0100

Dear Nick,

Thank you for your reply.

I have tried the commands with the alterations you suggested.

I am afraid I still have the same error even when I include the period(.).

. lrtest hetero . , df(20)
models hetero specified more than once
r(198);

Could this be an issue with my dataset? I have a very unbalanced panel
with many data points missing in the independent variables.

On 6 July 2012 19:24, Nick Cox <njcoxstata@gmail.com> wrote:
> The FAQ recommends different syntax. You omitted the period (.) in
>
> lrtest hetero . , df(`df')
>
> Nick
>
> On Fri, Jul 6, 2012 at 1:15 PM, Sean Lim <seanlim174@gmail.com> wrote:
>> Dear Statalisters,
>>
>> I am trying to test for heteroskedasticity in a panel dataset I have.
>> I am following the steps described in
>> http://www.stata.com/support/faqs/statistics/panel-level-heteroskedasticity-and-autocorrelation/
>>  but I am getting an error: " r(198) error when trying to use lrtest.
>>
>>
>> Any advice on how I should continue with this is appreciated. Below is
>> my output.
>>
>> Many thanks,
>>
>>
>> Sean
>>
>> . xtgls leverage avol7 time_tomaturity grade1 bid_ask_predict, igls
>> panels(heteroskedastic)
>> Iteration 1: tolerance = .03519474
>> Iteration 2: tolerance = .10619771
>> Iteration 3: tolerance = .13432693
>> Iteration 4: tolerance = .12540942
>> Iteration 5: tolerance = .0969322
>> Iteration 6: tolerance = .02952538
>> Iteration 7: tolerance = .01171261
>> Iteration 8: tolerance = .00374088
>> Iteration 9: tolerance = .00121751
>> Iteration 10: tolerance = .00043942
>> Iteration 11: tolerance = .00016508
>> Iteration 12: tolerance = .00006333
>> Iteration 13: tolerance = .00002464
>> Iteration 14: tolerance = 9.688e-06
>> Iteration 15: tolerance = 3.844e-06
>> Iteration 16: tolerance = 1.537e-06
>> Iteration 17: tolerance = 6.189e-07
>> Iteration 18: tolerance = 2.506e-07
>> Iteration 19: tolerance = 1.019e-07
>> Iteration 20: tolerance = 4.167e-08
>>
>>
>> Cross-sectional time-series FGLS regression
>>
>> Coefficients:  generalized least squares
>> Panels:        heteroskedastic
>> Correlation:   no autocorrelation
>>
>> Estimated covariances      =        21          Number of obs      =     15018
>> Estimated autocorrelations =         0          Number of groups   =        21
>> Estimated coefficients     =         5          Obs per group: min =       110
>>                                                                avg =  715.1429
>>                                                                max =       782
>>                                                 Wald chi2(4)       = 953523.91
>> Log likelihood             =  13896.44          Prob > chi2        =    0.0000
>>
>> ------------------------------------------------------------------------------
>>     leverage |      Coef.   Std. Err.      z    P>|z|     [95% Conf. Interval]
>> -------------+----------------------------------------------------------------
>>        avol7 |  -.7824862   .0049243  -158.90   0.000    -.7921376   -.7728347
>> time_tomat~y |  -.0002712   .0000154   -17.65   0.000    -.0003013   -.0002411
>>       grade1 |   -.399934   .0010845  -368.76   0.000    -.4020597   -.3978084
>> bid_ask_p~ct |   .0661513   .0043105    15.35   0.000     .0577029    .0745996
>>        _cons |   .9815676   .0009443  1039.42   0.000     .9797167    .9834184
>> ------------------------------------------------------------------------------
>>
>> . estimates store hetero
>>
>> . local df = e(N_g) - 1
>>
>> . di `df'
>> 20
>>
>> . lrtest hetero , df(20)
>> models hetero specified more than once
>> r(198);
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