Bivariate linear growth curve model used by the Portland Collective as the fulcrum of coordination has the following specification
where
- i - individual
- t - timepoint
- o - outcome (phys/cog)
- p - physical measure used in estimation
- c - cognitive measure used in estimation
- yti - score for the individual i at time t on an outcome
- β0i - bivariate initial status / random intercept
- β1i - bivariate rate of change / random slope
- u0i - is residual of the random intercept of an outcome
- u1i - is residual of the random slope of an outcome
- γ00 - o_GAMMA_00 - average initial status / common intercept of an outcome
- γ10 - o_GAMMA_10 - average rate of change / common slope of an outcome
- γ0k - o_GAMMA_0k - effect of the kth predictor on the random intercept of an outcome
- γ1k - o_GAMMA_1k - effect of the kth predictor on the random slope of an outcome
- ppτ00 - pp_TAU_00 - variance of physical intercept - p_cov_int
- ppτ11 - pp_TAU_11 - variance of physical slope - p_cov_slope
- ccτ11 - cc_TAU_11 - variance of cognitive slope
- ccτ00 - cc_TAU_00 - variance of cogntive intercept - var_int_cog
- ppτ01 - pp_TAU_01 - covariance btw physical intercept and physical slope
- pcτ01 - pc_TAU_01 - covariance btw physical intercept and cognitive slope
- pcτ00 - pc_TAU_00 - covariance btw physical intercept and cognitive intercept - I var_int_physical / corr_int
- pcτ11 - pc_TAU_11 - covariance btw physical slope and cognitive slope - S - var_slope_physical / corr_slope
- pcτ10 - pc_TAU_10 - covariance btw physical slope and cognitive intercept
- ccτ10 - cc_TAU_10 - covariance btw cognitive slope and cognitive intercept
- pσ - p_SIGMA - variance of the physical residual
- cσ - c_SIGMA - variance of the cogntive residual
- pcσ - pc_SIGMA - covariance btw physcial residual and cogntive residual - R - p_cov_res / corr_residual
THe model of this type could be fitted with the following Mplus syntax. To exemplify, we'll look at the model b1_female_aeh_tug_speed_tug_digitsymbolsubstitutiontest.out from ILSE study. This ILSE was specified in Mplus as follows
MODEL: ip sp | p1-p3 AT time1-time3;
ic sc | c1-c3 AT time1-time3;
ip; sp; ic; sc;
ip sp ic sc WITH ip sp ic sc;
ip sp ic sc ON Haupt second others Bage height;
p1-p3 (res_p);
c1-c3 (res_c);
p1-p3 pwith c1-c3(res_cov);
The output of this model is processed with MplusAutomation package and the following data object produced, containing the numeric results of the estimated model solution. The right-hand column contains alphanumeric names that map onto the algebraic specification of our bivariate growth model.
> message("Getting ", study, ", model ", i, ", ",out_file)
Getting ilse, model 97, b1_female_aeh_tug_speed_tug_digitsymbolsubstitutiontest.out
> model
paramHeader param est se est_se pval
1 IP.ON HAUPT -0.468 0.866 -0.541 0.589 - p_GAMMA_01
2 IP.ON SECOND 0.005 1.232 0.004 0.997 - p_GAMMA_02
3 IP.ON OTHERS -0.607 0.968 -0.627 0.531 - p_GAMMA_03
4 IP.ON BAGE -0.172 0.209 -0.821 0.411 - p_GAMMA_04
5 IP.ON HEIGHT -0.006 0.030 -0.216 0.829 - p_GAMMA_05
6 SP.ON HAUPT 0.111 0.138 0.806 0.420 - p_GAMMA_11
7 SP.ON SECOND 0.455 0.295 1.541 0.123 - p_GAMMA_12
8 SP.ON OTHERS 0.079 0.155 0.513 0.608 - p_GAMMA_13
9 SP.ON BAGE 0.007 0.023 0.315 0.753 - p_GAMMA_14
10 SP.ON HEIGHT 0.002 0.003 0.595 0.552 - p_GAMMA_15
11 IC.ON HAUPT 5.416 3.414 1.586 0.113 - c_GAMMA_01
12 IC.ON SECOND 14.395 10.836 1.328 0.184 - c_GAMMA_02
13 IC.ON OTHERS 15.247 4.121 3.700 0.000 - c_GAMMA_03
14 IC.ON BAGE -0.252 0.934 -0.270 0.787 - c_GAMMA_04
15 IC.ON HEIGHT 0.153 0.144 1.064 0.288 - c_GAMMA_05
16 SC.ON HAUPT -0.152 0.296 -0.513 0.608 - c_GAMMA_11
17 SC.ON SECOND -0.482 1.130 -0.426 0.670 - c_GAMMA_12
18 SC.ON OTHERS -0.166 0.318 -0.523 0.601 - c_GAMMA_13
19 SC.ON BAGE 0.049 0.055 0.886 0.376 - c_GAMMA_14
20 SC.ON HEIGHT 0.003 0.006 0.414 0.679 - c_GAMMA_15
21 IP.WITH SP -0.055 0.076 -0.731 0.465 - pp_TAU_01
22 IP.WITH IC -2.513 1.901 -1.322 0.186 - pc_TAU_00
23 IP.WITH SC -0.133 0.134 -0.994 0.320 - pc_TAU_01
24 SP.WITH IC 0.178 0.220 0.810 0.418 - pc_TAU_10
25 SP.WITH SC 0.001 0.017 0.078 0.938 - pc_TAU_11
26 IC.WITH SC -0.514 0.621 -0.827 0.408 - cc_TAU_10
27 P1.WITH C1 0.172 0.516 0.334 0.738 - pc_SIGMA
28 P2.WITH C2 0.172 0.516 0.334 0.738 - pc_SIGMA
29 P3.WITH C3 0.172 0.516 0.334 0.738 - pc_SIGMA
30 Intercepts P1 0.000 0.000 999.000 999.000
31 Intercepts P2 0.000 0.000 999.000 999.000
32 Intercepts P3 0.000 0.000 999.000 999.000
33 Intercepts C1 0.000 0.000 999.000 999.000
34 Intercepts C2 0.000 0.000 999.000 999.000
35 Intercepts C3 0.000 0.000 999.000 999.000
36 Intercepts IP 5.047 1.757 2.872 0.004 - p_GAMMA_00
37 Intercepts SP 0.151 0.216 0.700 0.484 - p_GAMMA_10
38 Intercepts IC 36.655 6.672 5.494 0.000 - c_GAMMA_00
39 Intercepts SC 0.062 0.451 0.137 0.891 - c_GAMMA_10
40 Residual.Variances P1 1.649 0.277 5.943 0.000 - p_SIGMA
41 Residual.Variances P2 1.649 0.277 5.943 0.000 - p_SIGMA
42 Residual.Variances P3 1.649 0.277 5.943 0.000 - p_SIGMA
43 Residual.Variances C1 14.190 1.094 12.973 0.000 - c_SIGMA
44 Residual.Variances C2 14.190 1.094 12.973 0.000 - c_SIGMA
45 Residual.Variances C3 14.190 1.094 12.973 0.000 - c_SIGMA
46 Residual.Variances IP 1.557 0.691 2.255 0.024 - pp_TAU_00
47 Residual.Variances SP 0.003 0.010 0.267 0.789 - pp_TAU_11
48 Residual.Variances IC 96.073 12.242 7.848 0.000 - cc_TAU_00
49 Residual.Variances SC 0.058 0.045 1.306 0.192 - cc_TAU_11
When variances and covariances are requested explicitly, the output will include additional elements of which we need to be aware during extraction. See b1_female_aeh_pulmonary_speed_fev_digitsymbol.out for example of the output with this option.
> message("Getting ", study, ", model ", i, ", ",out_file)
Getting radc, model 55, b1_female_aeh_pulmonary_speed_fev_digitsymbol.out
> model
paramHeader param est se est_se pval
1 IP.ON BAGE -0.022 0.002 -13.925 0.000
2 IP.ON EDUC 0.014 0.004 3.866 0.000
3 IP.ON HEIGHT 1.619 0.221 7.328 0.000
4 SP.ON BAGE 0.001 0.000 1.680 0.093
5 SP.ON EDUC 0.000 0.001 0.026 0.979
6 SP.ON HEIGHT -0.070 0.040 -1.748 0.080
7 IC.ON BAGE -0.007 0.011 -0.582 0.560
8 IC.ON EDUC 0.255 0.030 8.640 0.000
9 IC.ON HEIGHT 2.966 1.286 2.306 0.021
10 SC.ON BAGE -0.001 0.003 -0.336 0.737
11 SC.ON EDUC 0.001 0.008 0.104 0.917
12 SC.ON HEIGHT 0.310 0.362 0.857 0.392
13 SP.WITH IP 0.000 0.001 -0.082 0.935
14 IC.WITH IP 0.108 0.035 3.131 0.002
15 IC.WITH SP -0.004 0.008 -0.532 0.595
16 SC.WITH IP 0.003 0.011 0.319 0.750
17 SC.WITH SP 0.000 0.003 0.019 0.985
18 SC.WITH IC 0.066 0.083 0.800 0.424
19 P1.WITH C1 -0.013 0.007 -1.781 0.075
20 P2.WITH C2 -0.013 0.007 -1.781 0.075
21 P3.WITH C3 -0.013 0.007 -1.781 0.075
22 P4.WITH C4 -0.013 0.007 -1.781 0.075
23 P5.WITH C5 -0.013 0.007 -1.781 0.075
24 BAGE.WITH EDUC -1.096 0.783 -1.401 0.161
25 HEIGHT.WITH EDUC 0.038 0.008 4.849 0.000
26 HEIGHT.WITH BAGE -0.111 0.020 -5.580 0.000
27 Means EDUC 7.337 0.098 75.069 0.000
28 Means BAGE 8.665 0.250 34.638 0.000
29 Means HEIGHT -0.001 0.002 -0.418 0.676
30 Intercepts P1 0.000 0.000 999.000 999.000
31 Intercepts P2 0.000 0.000 999.000 999.000
32 Intercepts P3 0.000 0.000 999.000 999.000
33 Intercepts P4 0.000 0.000 999.000 999.000
34 Intercepts P5 0.000 0.000 999.000 999.000
35 Intercepts C1 0.000 0.000 999.000 999.000
36 Intercepts C2 0.000 0.000 999.000 999.000
37 Intercepts C3 0.000 0.000 999.000 999.000
38 Intercepts C4 0.000 0.000 999.000 999.000
39 Intercepts C5 0.000 0.000 999.000 999.000
40 Intercepts IP 1.611 0.032 50.425 0.000
41 Intercepts SP -0.038 0.008 -4.589 0.000
42 Intercepts IC 7.795 0.274 28.419 0.000
43 Intercepts SC 0.003 0.075 0.038 0.970
44 Variances EDUC 9.633 0.552 17.438 0.000
45 Variances BAGE 63.201 2.822 22.392 0.000
46 Variances HEIGHT 0.006 0.000 12.355 0.000
47 Residual.Variances P1 0.027 0.005 5.711 0.000
48 Residual.Variances P2 0.027 0.005 5.711 0.000
49 Residual.Variances P3 0.027 0.005 5.711 0.000
50 Residual.Variances P4 0.027 0.005 5.711 0.000
51 Residual.Variances P5 0.027 0.005 5.711 0.000
52 Residual.Variances C1 3.848 0.165 23.327 0.000
53 Residual.Variances C2 3.848 0.165 23.327 0.000
54 Residual.Variances C3 3.848 0.165 23.327 0.000
55 Residual.Variances C4 3.848 0.165 23.327 0.000
56 Residual.Variances C5 3.848 0.165 23.327 0.000
57 Residual.Variances IP 0.112 0.008 14.254 0.000
58 Residual.Variances SP 0.000 0.001 0.635 0.525
59 Residual.Variances IC 4.521 0.343 13.173 0.000
60 Residual.Variances SC 0.014 0.032 0.443 0.658