hi
I have a repeated design (experimental) with four measurement period (corresponding to baseline anticipation task and recovery) and two between-subject variables (gender as categorical and tas as continuous) and two covariates (age and imc both mean centered)
I ran a mixed model with a quadratic time variable with df method satterwait
I obtain the following result :
But when I try to interpret the quadratic interaction (the last interaction in the table), nothing appears to be significant.
the marginsplot evidenced the last interaction clearly on women but not on male but statistically I can't show this despite the significant interaction.
------------------ copy up to and including the previous line ------------------
any thoughts about potential explanations about this curiosity are welcome :-)
thanks
I have a repeated design (experimental) with four measurement period (corresponding to baseline anticipation task and recovery) and two between-subject variables (gender as categorical and tas as continuous) and two covariates (age and imc both mean centered)
I ran a mixed model with a quadratic time variable with df method satterwait
Code:
mixed RMSSD c.Time##c.Time##sex##c.tasc c.agec c.imcc||id:,dfmethod(sat) reml
Code:
Computing degrees of freedom ...
Mixed-effects REML regression Number of obs = 638
Group variable: id Number of groups = 176
Obs per group:
min = 1
avg = 3.6
max = 4
DF method: Satterthwaite DF: min = 171.12
avg = 450.91
max = 535.78
F(13, 392.89) = 8.01
Log restricted-likelihood = -2839.7673 Prob > F = 0.0000
------------------------------------------------------------------------------------------
RMSSD | Coefficient Std. err. t P>|t| [95% conf. interval]
-------------------------+----------------------------------------------------------------
Time | -28.45381 5.029226 -5.66 0.000 -38.33579 -18.57182
|
c.Time#c.Time | 6.248558 .9884281 6.32 0.000 4.306395 8.190721
|
1.sex | -4.594753 8.53208 -0.54 0.590 -21.35534 12.16583
|
sex#c.Time |
1 | 5.76347 7.716512 0.75 0.455 -9.399027 20.92597
|
sex#c.Time#c.Time |
1 | -1.138249 1.516564 -0.75 0.453 -4.118192 1.841694
|
tasc | -.0201683 .5492762 -0.04 0.971 -1.099175 1.058838
|
c.Time#c.tasc | .0004071 .5014809 0.00 0.999 -.9849501 .9857643
|
c.Time#c.Time#c.tasc | .0109818 .0986847 0.11 0.911 -.1829218 .2048855
|
sex#c.tasc |
1 | 2.248075 .8283858 2.71 0.007 .6207613 3.875389
|
sex#c.Time#c.tasc |
1 | -1.909282 .7528462 -2.54 0.012 -3.388609 -.4299562
|
sex#c.Time#c.Time#c.tasc |
1 | .3632271 .1479285 2.46 0.014 .0725516 .6539026
|
agec | -.2516221 .1102221 -2.28 0.024 -.4691768 -.0340673
imcc | -.2688028 .1942857 -1.38 0.168 -.6523081 .1147024
_cons | 79.28437 5.594944 14.17 0.000 68.29365 90.27508
------------------------------------------------------------------------------------------
------------------------------------------------------------------------------
Random-effects parameters | Estimate Std. err. [95% conf. interval]
-----------------------------+------------------------------------------------
id: Identity |
var(_cons) | 121.1566 24.23607 81.86031 179.3167
-----------------------------+------------------------------------------------
var(Residual) | 348.4228 22.96264 306.2024 396.4648
------------------------------------------------------------------------------
LR test vs. linear model: chibar2(01) = 48.51 Prob >= chibar2 = 0.0000
Code:
margins r.sex, at(Time=(1(1)4) tasc=(-10.17 0 10.17))
--------------------------------------------------------------
| Delta-method
| Contrast std. err. [95% conf. interval]
-------------+------------------------------------------------
sex@_at |
(1 vs 0) 1 | -7.109073 4.697893 -16.31677 2.098628
(1 vs 0) 2 | .0304682 3.349512 -6.534454 6.595391
(1 vs 0) 3 | 7.170009 4.674645 -1.992126 16.33214
(1 vs 0) 4 | 3.574994 4.02174 -4.30747 11.45746
(1 vs 0) 5 | 2.379192 2.873082 -3.251946 8.010329
(1 vs 0) 6 | 1.183389 4.061165 -6.776349 9.143126
(1 vs 0) 7 | 4.594524 4.03969 -3.323122 12.51217
(1 vs 0) 8 | 2.451417 2.887051 -3.207099 8.109932
(1 vs 0) 9 | .3083093 4.102824 -7.733077 8.349696
(1 vs 0) 10 | -4.050483 4.680018 -13.22315 5.122184
(1 vs 0) 11 | .2471437 3.330524 -6.280564 6.774851
(1 vs 0) 12 | 4.544771 4.67825 -4.624431 13.71397
--------------------------------------------------------------
Code:
* Example generated by -dataex-. For more info, type help dataex clear sex RMSSD IMC age tas id Time 0 . 26.38111803067427 47 42 301002 1 0 43.5690455299983 26.38111803067427 47 42 301002 2 0 40.131282806396484 26.38111803067427 47 42 301002 3 0 55.863792419433594 26.38111803067427 47 42 301002 4 1 . 30.399537242090112 32 41 301041 1 1 . 30.399537242090112 32 41 301041 2 1 . 30.399537242090112 32 41 301041 3 1 50.82164001464844 30.399537242090112 32 41 301041 4 0 . 21.95849147488975 41 52 301044 1 0 . 21.95849147488975 41 52 301044 2 0 . 21.95849147488975 41 52 301044 3 0 . 21.95849147488975 41 52 301044 4 0 . 22.747916891699425 21 32 301059 1 0 . 22.747916891699425 21 32 301059 2 0 . 22.747916891699425 21 32 301059 3 0 65.46923828125 22.747916891699425 21 32 301059 4 1 . 46.46006550768456 19 48 301061 1 1 . 46.46006550768456 19 48 301061 2 1 . 46.46006550768456 19 48 301061 3 1 48.13388442993164 46.46006550768456 19 48 301061 4 0 . 20.400316989540915 52 41 301062 1 0 . 20.400316989540915 52 41 301062 2 0 . 20.400316989540915 52 41 301062 3 0 66.44867706298828 20.400316989540915 52 41 301062 4 1 77.54911945186048 23.735447158870578 22 49 301063 1 1 . 23.735447158870578 22 49 301063 2 1 . 23.735447158870578 22 49 301063 3 1 84.45220947265625 23.735447158870578 22 49 301063 4 1 72.18422692921973 39.79048797855337 31 37 302004 1 1 . 39.79048797855337 31 37 302004 2 1 . 39.79048797855337 31 37 302004 3 1 66.5587387084961 39.79048797855337 31 37 302004 4 0 49.842341247133774 32.6294267034245 29 64 302009 1 0 . 32.6294267034245 29 64 302009 2 0 . 32.6294267034245 29 64 302009 3 0 54.345741271972656 32.6294267034245 29 64 302009 4 1 91.86158985474708 30.561683908094352 26 44 302011 1 1 . 30.561683908094352 26 44 302011 2 1 . 30.561683908094352 26 44 302011 3 1 73.03433227539063 30.561683908094352 26 44 302011 4 1 25.646122754270216 46.13384559828077 40 57 302015 1 1 34.4880398501258 46.13384559828077 40 57 302015 2 1 39.5731086730957 46.13384559828077 40 57 302015 3 1 35.33453369140625 46.13384559828077 40 57 302015 4 1 89.91885910622081 26.482243560432856 22 70 302016 1 1 52.1906913488704 26.482243560432856 22 70 302016 2 1 49.85567855834961 26.482243560432856 22 70 302016 3 1 93.59951782226563 26.482243560432856 22 70 302016 4 0 34.96221411582996 40.49355608620519 50 37 302023 1 0 . 40.49355608620519 50 37 302023 2 0 . 40.49355608620519 50 37 302023 3 0 44.75213623046875 40.49355608620519 50 37 302023 4 0 58.31698073987165 22.321492704288158 54 35 302026 1 0 . 22.321492704288158 54 35 302026 2 0 . 22.321492704288158 54 35 302026 3 0 66.51414489746094 22.321492704288158 54 35 302026 4 1 60.96224235348996 37.28335203890759 25 58 302035 1 1 29.8621632215506 37.28335203890759 25 58 302035 2 1 32.76686096191406 37.28335203890759 25 58 302035 3 1 60.282371520996094 37.28335203890759 25 58 302035 4 1 42.15874900642676 39.312358840437454 55 45 302036 1 1 62.0336049379118 39.312358840437454 55 45 302036 2 1 39.79743576049805 39.312358840437454 55 45 302036 3 1 37.10237121582031 39.312358840437454 55 45 302036 4 1 40.81092850942878 26.22581334108242 23 45 302039 1 1 60.2726797012324 26.22581334108242 23 45 302039 2 1 43.35675811767578 26.22581334108242 23 45 302039 3 1 40.3941650390625 26.22581334108242 23 45 302039 4 1 57.88388640065131 43.545985572969016 22 36 302040 1 1 74.0354782014699 43.545985572969016 22 36 302040 2 1 53.070613861083984 43.545985572969016 22 36 302040 3 1 53.1945686340332 43.545985572969016 22 36 302040 4 0 62.02567908400774 22.07612456747405 25 54 302047 1 0 28.0767906435103 22.07612456747405 25 54 302047 2 0 61.1196174621582 22.07612456747405 25 54 302047 3 0 77.34635925292969 22.07612456747405 25 54 302047 4 1 37.071829154198184 33.48218806662551 36 36 303002 1 1 70.7923247729106 33.48218806662551 36 36 303002 2 1 69.3332748413086 33.48218806662551 36 36 303002 3 1 37.811553955078125 33.48218806662551 36 36 303002 4 end
any thoughts about potential explanations about this curiosity are welcome :-)
thanks
