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Re: st: Repeated measures


From   David Airey <david.airey@vanderbilt.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Repeated measures
Date   Sat, 14 Mar 2009 15:00:20 -0500

.

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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