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Re: st: Repeated measures


From   Nikolaos Pandis <npandis@yahoo.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Repeated measures
Date   Sat, 14 Mar 2009 13:48:36 -0700 (PDT)

Dear David,

That was great! Thank you very much.

Nikolaos
--- On Sat, 3/14/09, David Airey <david.airey@vanderbilt.edu> wrote:


From: David Airey <david.airey@vanderbilt.edu>
Subject: Re: st: Repeated measures
To: statalist@hsphsun2.harvard.edu
Date: Saturday, March 14, 2009, 10:00 PM


.

You don't need statistics for these data. Just plot them.

clear

input str1 wiretype wireno trial force
A    1    1    1.42016
A    1    2    1.47212
A    1    3    1.44614
A    1    4    1.43748
A    1    5    1.52407
A    2    1    1.50675
A    2    2    1.44614
A    2    3    1.43748
A    2    4    1.4115
A    2    5    1.43748
A    3    1    1.42016
A    3    2    1.38552
A    3    3    1.47212
A    3    4    1.40284
A    3    5    1.40284
A    4    1    1.49809
A    4    2    1.42016
A    4    3    1.24697
A    4    4    1.34222
A    4    5    1.31625
A    5    1    1.42882
A    5    2    1.54139
A    5    3    1.42882
A    5    4    1.43748
A    5    5    1.54139
B    1    1    1.26429
B    1    2    1.17769
B    1    3    1.35088
B    1    4    1.3249
B    1    5    1.29893
B    2    1    1.1344
B    2    2    1.14306
B    2    3    1.52407
B    2    4    1.42882
B    2    5    1.43748
B    3    1    1.29893
B    3    2    1.24697
B    3    3    1.22965
B    3    4    1.30759
B    3    5    1.29027
B    4    1    1.29027
B    4    2    1.16037
B    4    3    1.16037
B    4    4    1.35088
B    4    5    1.35088
B    5    1    1.43748
B    5    2    1.39418
B    5    3    1.46346
B    5    4    1.54139
B    5    5    1.54139
C    1    1    9.5168
C    1    2    9.24835
C    1    3    9.31763
C    1    4    9.27433
C    1    5    9.24835
C    2    1    9.25701
C    2    2    9.30897
C    2    3    9.4735
C    2    4    9.22238
C    2    5    9.24835
C    3    1    9.11846
C    3    2    9.07516
C    3    3    9.16176
C    3    4    9.07516
C    3    5    9.12712
C    4    1    9.5601
C    4    2    9.71597
C    4    3    9.84586
C    4    4    9.67267
C    4    5    9.17908
C    5    1    9.23104
C    5    2    9.17908
C    5    3    9.22238
C    5    4    9.17908
C    5    5    9.21372
D    1    1    1.02182
D    1    2    0.94389
D    1    3    1.01316
D    1    4    1.0045
D    1    5    0.96121
D    2    1    0.83997
D    2    2    0.83131
D    2    3    1.01316
D    2    4    1.08244
D    2    5    1.08244
D    3    1    0.83997
D    3    2    0.85812
D    3    3    0.9274
D    3    4    0.89276
D    3    5    0.78802
D    4    1    1.10284
D    4    2    1.02099
D    4    3    1.16903
D    4    4    1.16037
D    4    5    1.06512
D    5    1    1.0478
D    5    2    1.02182
D    5    3    0.95255
D    5    4    1.1344
D    5    5    0.98718
end

encode wiretype, gen(type)
anova force type / wireno|type /

. anova force type / wireno|type /

                            Number of obs =     100     R-squared      
=  0.9994
                            Root MSE      = .096737     Adj R-squared  
=  0.9992

                   Source |  Partial SS    df       MS           F      
Prob > F
              ------------ 
+----------------------------------------------------
                    Model |  1220.86069    19   64.255826     
6866.37     0.0000
                          |
                     type |  1219.85261     3  406.617537     
6453.71     0.0000
              wireno|type |  1.00808338    16  .063005211
              ------------ 
+----------------------------------------------------
              wireno|type |  1.00808338    16  .063005211        
6.73     0.0000
                          |
                 Residual |  .748644327    80  .009358054
              ------------ 
+----------------------------------------------------
                    Total |  1221.60934    99  12.3394883

Follow

http://www.stata.com/support/faqs/stat/singledof.html

for post hoc tests if you feel you really need to do them.

-Dave

On Mar 14, 2009, at 2:21 PM, Nikolaos Pandis wrote:

> Dear all,
>
> Thank you for your responses.
> I apologize for the confusion on my data setup.
> I am posting my exact data setup ( I hope it shows ok on the sent  
> email):
>
> WireType    wireno    trial    IntrusionForce (N)
> A    1    1    1.42016
> A    1    2    1.47212
> A    1    3    1.44614
> A    1    4    1.43748
> A    1    5    1.52407
> A    2    1    1.50675
> A    2    2    1.44614
> A    2    3    1.43748
> A    2    4    1.4115
> A    2    5    1.43748
> A    3    1    1.42016
> A    3    2    1.38552
> A    3    3    1.47212
> A    3    4    1.40284
> A    3    5    1.40284
> A    4    1    1.49809
> A    4    2    1.42016
> A    4    3    1.24697
> A    4    4    1.34222
> A    4    5    1.31625
> A    5    1    1.42882
> A    5    2    1.54139
> A    5    3    1.42882
> A    5    4    1.43748
> A    5    5    1.54139
> B    1    1    1.26429
> B    1    2    1.17769
> B    1    3    1.35088
> B    1    4    1.3249
> B    1    5    1.29893
> B    2    1    1.1344
> B    2    2    1.14306
> B    2    3    1.52407
> B    2    4    1.42882
> B    2    5    1.43748
> B    3    1    1.29893
> B    3    2    1.24697
> B    3    3    1.22965
> B    3    4    1.30759
> B    3    5    1.29027
> B    4    1    1.29027
> B    4    2    1.16037
> B    4    3    1.16037
> B    4    4    1.35088
> B    4    5    1.35088
> B    5    1    1.43748
> B    5    2    1.39418
> B    5    3    1.46346
> B    5    4    1.54139
> B    5    5    1.54139
> C    1    1    9.5168
> C    1    2    9.24835
> C    1    3    9.31763
> C    1    4    9.27433
> C    1    5    9.24835
> C    2    1    9.25701
> C    2    2    9.30897
> C    2    3    9.4735
> C    2    4    9.22238
> C    2    5    9.24835
> C    3    1    9.11846
> C    3    2    9.07516
> C    3    3    9.16176
> C    3    4    9.07516
> C    3    5    9.12712
> C    4    1    9.5601
> C    4    2    9.71597
> C    4    3    9.84586
> C    4    4    9.67267
> C    4    5    9.17908
> C    5    1    9.23104
> C    5    2    9.17908
> C    5    3    9.22238
> C    5    4    9.17908
> C    5    5    9.21372
> D    1    1    1.02182
> D    1    2    0.94389
> D    1    3    1.01316
> D    1    4    1.0045
> D    1    5    0.96121
> D    2    1    0.83997
> D    2    2    0.83131
> D    2    3    1.01316
> D    2    4    1.08244
> D    2    5    1.08244
> D    3    1    0.83997
> D    3    2    0.85812
> D    3    3    0.9274
> D    3    4    0.89276
> D    3    5    0.78802
> D    4    1    1.10284
> D    4    2    1.02099
> D    4    3    1.16903
> D    4    4    1.16037
> D    4    5    1.06512
> D    5    1    1.0478
> D    5    2    1.02182
> D    5    3    0.95255
> D    5    4    1.1344
> D    5    5    0.98718
>
> Thank you very much for your help.
> Best wishes,
>
> Nikolaos
>
>
> --- On Sat, 3/14/09, David Airey <david.airey@vanderbilt.edu> wrote:
>
>
> From: David Airey <david.airey@vanderbilt.edu>
> Subject: Re: st: Repeated measures
> To: statalist@hsphsun2.harvard.edu
> Date: Saturday, March 14, 2009, 6:33 PM
>
>
> .
>
> I think measurements nested in wire is the residual in the model
>
> anova force wiretype / wireno|wiretype /
>
> -Dave
>
>
> On Mar 14, 2009, at 11:26 AM, TA Stat wrote:
>
>> I think it is measurements nested in specimen nested in wiretype.
>> Your main objective is to identify whether variation among wiretype  
>> is
>> significant or not.  Right?
>>
>> Pete
>>
>> On Sat, Mar 14, 2009 at 11:12 PM, David Airey
>> <david.airey@vanderbilt.edu> wrote:
>>> .
>>>
>>> I was confused by your data layout.
>>>
>>> Your data are really just 3 columns wide:
>>>
>>> WireType WireNo Force
>>>
>>> where wiretype and wireno are replicated 5 times,
>>>
>>> So
>>>
>>> anova force wiretype / wireno|wiretype /
>>>
>>> is fine, or the equivalent xtmixed...
>>>
>>> -Dave
>>>
>>> On Mar 14, 2009, at 3:16 AM, Nikolaos Pandis wrote:
>>>
>>>> Dear Statalisters,
>>>>
>>>> I have the following dataset (except I have it in long format-one
>>>> measurement per row) :
>>>>
>>>> WireType        WireNo  Trial           Force
>>>>
>>>> A       A1      1,2,3,4,5             5 measurements-1 per trial
>>>> A       A2      1,2,3,4,5             5 measurements-1 per trial
>>>> A       A3      1,2,3,4,5             5 measurements-1 per trial
>>>> A       A4      1,2,3,4,5             5 measurements-1 per trial
>>>> A       A5      1,2,3,4,5             5 measurements-1 per trial
>>>>
>>>> B       B1      1,2,3,4,5             5 measurements-1 per trial
>>>> B       B2      1,2,3,4,5             5 measurements-1 per trial
>>>> B       B3      1,2,3,4,5             5 measurements-1 per trial
>>>> B       B4      1,2,3,4,5             5 measurements-1 per trial
>>>> B       B5      1,2,3,4,5             5 measurements-1 per trial
>>>>
>>>>
>>>> C       C1      1,2,3,4,5             5 measurements-1 per trial
>>>> C       C2      1,2,3,4,5             5 measurements-1 per trial
>>>> C       C3      1,2,3,4,5             5 measurements-1 per trial
>>>> C       C4      1,2,3,4,5             5 measurements-1 per trial
>>>> C       C5      1,2,3,4,5             5 measurements-1 per trial
>>>>
>>>> D       D1      1,2,3,4,5             5 measurements-1 per trial
>>>> D       D2      1,2,3,4,5             5 measurements-1 per trial
>>>> D       D3      1,2,3,4,5             5 measurements-1 per trial
>>>> D       D4      1,2,3,4,5             5 measurements-1 per trial
>>>> D       D5      1,2,3,4,5             5 measurements-1 per trial
>>>>
>>>> I am testing the forces generated by 4 different wiretypes to see
>>>> if there
>>>> are significant differences.
>>>> For each wiretype (categorical A B C D) I am using 5 specimens
>>>> (A1-5,..D1-5) and for each specimen I am repeating the measurement
>>>> 5 times.
>>>> The outcome is force and it is a continuous variable.
>>>>
>>>> This looks like a repeated measures with each trial nested in the
>>>> WireNo
>>>> and the WireNo nested inside WireType?
>>>>
>>>> I was trying to use the xtgee command but I was not sure how to
>>>> construct
>>>> it:
>>>> xi:xtreg force i.xxxxx i.yyyyyy, i(zzzzz) ?
>>>>
>>>> Any help would be appreciated.
>>>>
>>>> Thank you very much,
>>>>
>>>> Nikolaos
>>>>
>>>>
>>>>
>>>>
>>>> *
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>>>
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