The Basic Syntax
modsem introduces a new feature to the
lavaan syntax—the semicolon operator (:). The
semicolon operator works the same way as in the lm()
function. To specify an interaction effect between two variables, you
join them by Var1:Var2.
Models can be estimated using one of the product indicator approaches
("ca", "rca", "dblcent",
"pind") or by using the latent moderated structural
equations approach ("lms") or the quasi maximum likelihood
approach ("qml"). The product indicator approaches are
estimated via lavaan, while the lms and
qml approaches are estimated via modsem
itself.
A Simple Example
Here is a simple example of how to specify an interaction effect
between two latent variables in lavaan.
m1 <- '
# Outer Model
X =~ x1 + x2 + x3
Y =~ y1 + y2 + y3
Z =~ z1 + z2 + z3
# Inner Model
Y ~ X + Z + X:Z
'
est1 <- modsem(m1, oneInt)
summary(est1)
#> modsem (version 1.0.4, approach = dblcent):
#> lavaan 0.6-19 ended normally after 159 iterations
#>
#> Estimator ML
#> Optimization method NLMINB
#> Number of model parameters 60
#>
#> Number of observations 2000
#>
#> Model Test User Model:
#>
#> Test statistic 122.924
#> Degrees of freedom 111
#> P-value (Chi-square) 0.207
#>
#> Parameter Estimates:
#>
#> Standard errors Standard
#> Information Expected
#> Information saturated (h1) model Structured
#>
#> Latent Variables:
#> Estimate Std.Err z-value P(>|z|)
#> X =~
#> x1 1.000
#> x2 0.804 0.013 63.612 0.000
#> x3 0.916 0.014 67.144 0.000
#> Y =~
#> y1 1.000
#> y2 0.798 0.007 107.428 0.000
#> y3 0.899 0.008 112.453 0.000
#> Z =~
#> z1 1.000
#> z2 0.812 0.013 64.763 0.000
#> z3 0.882 0.013 67.014 0.000
#> XZ =~
#> x1z1 1.000
#> x2z1 0.805 0.013 60.636 0.000
#> x3z1 0.877 0.014 62.680 0.000
#> x1z2 0.793 0.013 59.343 0.000
#> x2z2 0.646 0.015 43.672 0.000
#> x3z2 0.706 0.016 44.292 0.000
#> x1z3 0.887 0.014 63.700 0.000
#> x2z3 0.716 0.016 45.645 0.000
#> x3z3 0.781 0.017 45.339 0.000
#>
#> Regressions:
#> Estimate Std.Err z-value P(>|z|)
#> Y ~
#> X 0.675 0.027 25.379 0.000
#> Z 0.561 0.026 21.606 0.000
#> XZ 0.702 0.027 26.360 0.000
#>
#> Covariances:
#> Estimate Std.Err z-value P(>|z|)
#> .x1z1 ~~
#> .x2z2 0.000
#> .x2z3 0.000
#> .x3z2 0.000
#> .x3z3 0.000
#> .x2z1 ~~
#> .x1z2 0.000
#> .x1z2 ~~
#> .x2z3 0.000
#> .x3z1 ~~
#> .x1z2 0.000
#> .x1z2 ~~
#> .x3z3 0.000
#> .x2z1 ~~
#> .x1z3 0.000
#> .x2z2 ~~
#> .x1z3 0.000
#> .x3z1 ~~
#> .x1z3 0.000
#> .x3z2 ~~
#> .x1z3 0.000
#> .x2z1 ~~
#> .x3z2 0.000
#> .x3z3 0.000
#> .x3z1 ~~
#> .x2z2 0.000
#> .x2z2 ~~
#> .x3z3 0.000
#> .x3z1 ~~
#> .x2z3 0.000
#> .x3z2 ~~
#> .x2z3 0.000
#> .x1z1 ~~
#> .x1z2 0.115 0.008 14.802 0.000
#> .x1z3 0.114 0.008 13.947 0.000
#> .x2z1 0.125 0.008 16.095 0.000
#> .x3z1 0.140 0.009 16.135 0.000
#> .x1z2 ~~
#> .x1z3 0.103 0.007 14.675 0.000
#> .x2z2 0.128 0.006 20.850 0.000
#> .x3z2 0.146 0.007 21.243 0.000
#> .x1z3 ~~
#> .x2z3 0.116 0.007 17.818 0.000
#> .x3z3 0.135 0.007 18.335 0.000
#> .x2z1 ~~
#> .x2z2 0.135 0.006 20.905 0.000
#> .x2z3 0.145 0.007 21.145 0.000
#> .x3z1 0.114 0.007 16.058 0.000
#> .x2z2 ~~
#> .x2z3 0.117 0.006 20.419 0.000
#> .x3z2 0.116 0.006 20.586 0.000
#> .x2z3 ~~
#> .x3z3 0.109 0.006 18.059 0.000
#> .x3z1 ~~
#> .x3z2 0.138 0.007 19.331 0.000
#> .x3z3 0.158 0.008 20.269 0.000
#> .x3z2 ~~
#> .x3z3 0.131 0.007 19.958 0.000
#> X ~~
#> Z 0.201 0.024 8.271 0.000
#> XZ 0.016 0.025 0.628 0.530
#> Z ~~
#> XZ 0.062 0.025 2.449 0.014
#>
#> Variances:
#> Estimate Std.Err z-value P(>|z|)
#> .x1 0.160 0.009 17.871 0.000
#> .x2 0.162 0.007 22.969 0.000
#> .x3 0.163 0.008 20.161 0.000
#> .y1 0.159 0.009 17.896 0.000
#> .y2 0.154 0.007 22.640 0.000
#> .y3 0.164 0.008 20.698 0.000
#> .z1 0.168 0.009 18.143 0.000
#> .z2 0.158 0.007 22.264 0.000
#> .z3 0.158 0.008 20.389 0.000
#> .x1z1 0.311 0.014 22.227 0.000
#> .x2z1 0.292 0.011 27.287 0.000
#> .x3z1 0.327 0.012 26.275 0.000
#> .x1z2 0.290 0.011 26.910 0.000
#> .x2z2 0.239 0.008 29.770 0.000
#> .x3z2 0.270 0.009 29.117 0.000
#> .x1z3 0.272 0.012 23.586 0.000
#> .x2z3 0.245 0.009 27.979 0.000
#> .x3z3 0.297 0.011 28.154 0.000
#> X 0.981 0.036 26.895 0.000
#> .Y 0.990 0.038 25.926 0.000
#> Z 1.016 0.038 26.856 0.000
#> XZ 1.045 0.044 24.004 0.000By default, the model is estimated using the "dblcent"
method. If you want to use another method, you can change it using the
method argument.
est1 <- modsem(m1, oneInt, method = "lms")
summary(est1)
#>
#> modsem (version 1.0.4):
#> Estimator LMS
#> Optimization method EM-NLMINB
#> Number of observations 2000
#> Number of iterations 92
#> Loglikelihood -14687.85
#> Akaike (AIC) 29437.71
#> Bayesian (BIC) 29611.34
#>
#> Numerical Integration:
#> Points of integration (per dim) 24
#> Dimensions 1
#> Total points of integration 24
#>
#> Fit Measures for H0:
#> Loglikelihood -17832
#> Akaike (AIC) 35723.75
#> Bayesian (BIC) 35891.78
#> Chi-square 17.52
#> Degrees of Freedom (Chi-square) 24
#> P-value (Chi-square) 0.826
#> RMSEA 0.000
#>
#> Comparative fit to H0 (no interaction effect)
#> Loglikelihood change 3144.02
#> Difference test (D) 6288.04
#> Degrees of freedom (D) 1
#> P-value (D) 0.000
#>
#> R-Squared:
#> Y 0.596
#> R-Squared Null-Model (H0):
#> Y 0.395
#> R-Squared Change:
#> Y 0.201
#>
#> Parameter Estimates:
#> Coefficients unstandardized
#> Information expected
#> Standard errors standard
#>
#> Latent Variables:
#> Estimate Std.Error z.value P(>|z|)
#> X =~
#> x1 1.000
#> x2 0.804 0.012 65.27 0.000
#> x3 0.915 0.013 68.77 0.000
#> Z =~
#> z1 1.000
#> z2 0.810 0.012 65.55 0.000
#> z3 0.881 0.013 69.05 0.000
#> Y =~
#> y1 1.000
#> y2 0.799 0.008 106.30 0.000
#> y3 0.899 0.008 112.47 0.000
#>
#> Regressions:
#> Estimate Std.Error z.value P(>|z|)
#> Y ~
#> X 0.676 0.032 20.89 0.000
#> Z 0.572 0.029 19.53 0.000
#> X:Z 0.712 0.027 26.72 0.000
#>
#> Intercepts:
#> Estimate Std.Error z.value P(>|z|)
#> x1 1.025 0.021 48.95 0.000
#> x2 1.218 0.018 68.87 0.000
#> x3 0.922 0.020 47.18 0.000
#> z1 1.016 0.028 36.17 0.000
#> z2 1.209 0.023 51.86 0.000
#> z3 0.920 0.025 36.75 0.000
#> y1 1.046 0.035 29.91 0.000
#> y2 1.227 0.029 42.98 0.000
#> y3 0.962 0.032 30.17 0.000
#> Y 0.000
#> X 0.000
#> Z 0.000
#>
#> Covariances:
#> Estimate Std.Error z.value P(>|z|)
#> X ~~
#> Z 0.198 0.027 7.23 0.000
#>
#> Variances:
#> Estimate Std.Error z.value P(>|z|)
#> x1 0.160 0.008 19.63 0.000
#> x2 0.163 0.007 24.10 0.000
#> x3 0.165 0.008 21.53 0.000
#> z1 0.166 0.009 18.74 0.000
#> z2 0.160 0.007 22.64 0.000
#> z3 0.158 0.008 20.78 0.000
#> y1 0.160 0.009 17.98 0.000
#> y2 0.154 0.007 22.74 0.000
#> y3 0.163 0.008 20.73 0.000
#> X 0.972 0.032 30.84 0.000
#> Z 1.017 0.038 26.66 0.000
#> Y 0.984 0.036 27.12 0.000Interactions Between Two Observed Variables
modsem allows you to estimate interactions between not
only latent variables but also observed variables. Below, we first run a
regression with only observed variables, where there is an interaction
between x1 and z2, and then run an equivalent
model using modsem().
Using a Regression
reg1 <- lm(y1 ~ x1*z1, oneInt)
summary(reg1)
#>
#> Call:
#> lm(formula = y1 ~ x1 * z1, data = oneInt)
#>
#> Residuals:
#> Min 1Q Median 3Q Max
#> -3.7155 -0.8087 -0.0367 0.8078 4.6531
#>
#> Coefficients:
#> Estimate Std. Error t value Pr(>|t|)
#> (Intercept) 0.51422 0.04618 11.135 <2e-16 ***
#> x1 0.05477 0.03387 1.617 0.1060
#> z1 -0.06575 0.03461 -1.900 0.0576 .
#> x1:z1 0.54361 0.02272 23.926 <2e-16 ***
#> ---
#> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
#>
#> Residual standard error: 1.184 on 1996 degrees of freedom
#> Multiple R-squared: 0.4714, Adjusted R-squared: 0.4706
#> F-statistic: 593.3 on 3 and 1996 DF, p-value: < 2.2e-16Using modsem
When you have interactions between observed variables, it is
generally recommended to use method = "pind". Interaction
effects with observed variables are not supported by the
LMS and QML approaches. In some cases, you can
define a latent variable with a single indicator to estimate the
interaction effect between two observed variables in the
LMS and QML approaches, but this is generally
not recommended.
# Using "pind" as the method (see Chapter 3)
est2 <- modsem('y1 ~ x1 + z1 + x1:z1', data = oneInt, method = "pind")
summary(est2)
#> modsem (version 1.0.4, approach = pind):
#> lavaan 0.6-19 ended normally after 1 iteration
#>
#> Estimator ML
#> Optimization method NLMINB
#> Number of model parameters 4
#>
#> Number of observations 2000
#>
#> Model Test User Model:
#>
#> Test statistic 0.000
#> Degrees of freedom 0
#>
#> Parameter Estimates:
#>
#> Standard errors Standard
#> Information Expected
#> Information saturated (h1) model Structured
#>
#> Regressions:
#> Estimate Std.Err z-value P(>|z|)
#> y1 ~
#> x1 0.055 0.034 1.619 0.105
#> z1 -0.066 0.035 -1.902 0.057
#> x1z1 0.544 0.023 23.950 0.000
#>
#> Variances:
#> Estimate Std.Err z-value P(>|z|)
#> .y1 1.399 0.044 31.623 0.000Interactions Between Latent and Observed Variables
modsem also allows you to estimate interaction effects
between latent and observed variables. To do so, simply join a latent
and an observed variable with a colon (e.g.,
'latent:observer'). As with interactions between observed
variables, it is generally recommended to use
method = "pind" for estimating the effect between latent
and observed variables.
m3 <- '
# Outer Model
X =~ x1 + x2 + x3
Y =~ y1 + y2 + y3
# Inner Model
Y ~ X + z1 + X:z1
'
est3 <- modsem(m3, oneInt, method = "pind")
summary(est3)
#> modsem (version 1.0.4, approach = pind):
#> lavaan 0.6-19 ended normally after 45 iterations
#>
#> Estimator ML
#> Optimization method NLMINB
#> Number of model parameters 22
#>
#> Number of observations 2000
#>
#> Model Test User Model:
#>
#> Test statistic 4468.171
#> Degrees of freedom 32
#> P-value (Chi-square) 0.000
#>
#> Parameter Estimates:
#>
#> Standard errors Standard
#> Information Expected
#> Information saturated (h1) model Structured
#>
#> Latent Variables:
#> Estimate Std.Err z-value P(>|z|)
#> X =~
#> x1 1.000
#> x2 0.803 0.013 63.697 0.000
#> x3 0.915 0.014 67.548 0.000
#> Y =~
#> y1 1.000
#> y2 0.798 0.007 115.375 0.000
#> y3 0.899 0.007 120.783 0.000
#> Xz1 =~
#> x1z1 1.000
#> x2z1 0.947 0.010 96.034 0.000
#> x3z1 0.902 0.009 99.512 0.000
#>
#> Regressions:
#> Estimate Std.Err z-value P(>|z|)
#> Y ~
#> X 0.021 0.034 0.614 0.540
#> z1 -0.185 0.023 -8.096 0.000
#> Xz1 0.646 0.017 37.126 0.000
#>
#> Covariances:
#> Estimate Std.Err z-value P(>|z|)
#> X ~~
#> Xz1 1.243 0.055 22.523 0.000
#>
#> Variances:
#> Estimate Std.Err z-value P(>|z|)
#> .x1 0.158 0.009 17.976 0.000
#> .x2 0.164 0.007 23.216 0.000
#> .x3 0.162 0.008 20.325 0.000
#> .y1 0.158 0.009 17.819 0.000
#> .y2 0.154 0.007 22.651 0.000
#> .y3 0.164 0.008 20.744 0.000
#> .x1z1 0.315 0.017 18.328 0.000
#> .x2z1 0.428 0.019 22.853 0.000
#> .x3z1 0.337 0.016 21.430 0.000
#> X 0.982 0.036 26.947 0.000
#> .Y 1.112 0.040 27.710 0.000
#> Xz1 3.965 0.136 29.217 0.000Quadratic Effects
Quadratic effects are essentially a special case of interaction
effects. Thus, modsem can also be used to estimate
quadratic effects.
m4 <- '
# Outer Model
X =~ x1 + x2 + x3
Y =~ y1 + y2 + y3
Z =~ z1 + z2 + z3
# Inner Model
Y ~ X + Z + Z:X + X:X
'
est4 <- modsem(m4, oneInt, method = "qml")
summary(est4)
#>
#> modsem (version 1.0.4):
#> Estimator QML
#> Optimization method NLMINB
#> Number of observations 2000
#> Number of iterations 123
#> Loglikelihood -17496.2
#> Akaike (AIC) 35056.4
#> Bayesian (BIC) 35235.63
#>
#> Fit Measures for H0:
#> Loglikelihood -17832
#> Akaike (AIC) 35723.75
#> Bayesian (BIC) 35891.78
#> Chi-square 17.52
#> Degrees of Freedom (Chi-square) 24
#> P-value (Chi-square) 0.826
#> RMSEA 0.000
#>
#> Comparative fit to H0 (no interaction effect)
#> Loglikelihood change 335.68
#> Difference test (D) 671.35
#> Degrees of freedom (D) 2
#> P-value (D) 0.000
#>
#> R-Squared:
#> Y 0.607
#> R-Squared Null-Model (H0):
#> Y 0.395
#> R-Squared Change:
#> Y 0.212
#>
#> Parameter Estimates:
#> Coefficients unstandardized
#> Information observed
#> Standard errors standard
#>
#> Latent Variables:
#> Estimate Std.Error z.value P(>|z|)
#> X =~
#> x1 1.000
#> x2 0.803 0.013 63.961 0.000
#> x3 0.914 0.013 67.797 0.000
#> Z =~
#> z1 1.000
#> z2 0.810 0.012 65.124 0.000
#> z3 0.881 0.013 67.621 0.000
#> Y =~
#> y1 1.000
#> y2 0.798 0.007 107.567 0.000
#> y3 0.899 0.008 112.542 0.000
#>
#> Regressions:
#> Estimate Std.Error z.value P(>|z|)
#> Y ~
#> X 0.674 0.032 20.888 0.000
#> Z 0.566 0.030 18.948 0.000
#> X:X -0.005 0.023 -0.207 0.836
#> X:Z 0.713 0.029 24.554 0.000
#>
#> Intercepts:
#> Estimate Std.Error z.value P(>|z|)
#> x1 1.023 0.024 42.894 0.000
#> x2 1.216 0.020 60.996 0.000
#> x3 0.919 0.022 41.484 0.000
#> z1 1.012 0.024 41.576 0.000
#> z2 1.206 0.020 59.271 0.000
#> z3 0.916 0.022 42.063 0.000
#> y1 1.042 0.038 27.684 0.000
#> y2 1.224 0.030 40.159 0.000
#> y3 0.958 0.034 28.101 0.000
#> Y 0.000
#> X 0.000
#> Z 0.000
#>
#> Covariances:
#> Estimate Std.Error z.value P(>|z|)
#> X ~~
#> Z 0.200 0.024 8.239 0.000
#>
#> Variances:
#> Estimate Std.Error z.value P(>|z|)
#> x1 0.158 0.009 18.145 0.000
#> x2 0.162 0.007 23.188 0.000
#> x3 0.165 0.008 20.821 0.000
#> z1 0.166 0.009 18.341 0.000
#> z2 0.159 0.007 22.622 0.000
#> z3 0.158 0.008 20.714 0.000
#> y1 0.159 0.009 17.975 0.000
#> y2 0.154 0.007 22.670 0.000
#> y3 0.164 0.008 20.711 0.000
#> X 0.983 0.036 26.994 0.000
#> Z 1.019 0.038 26.951 0.000
#> Y 0.943 0.038 24.820 0.000More Complicated Examples
Here is a more complex example using the theory of planned behavior (TPB) model.
tpb <- '
# Outer Model (Based on Hagger et al., 2007)
ATT =~ att1 + att2 + att3 + att4 + att5
SN =~ sn1 + sn2
PBC =~ pbc1 + pbc2 + pbc3
INT =~ int1 + int2 + int3
BEH =~ b1 + b2
# Inner Model (Based on Steinmetz et al., 2011)
INT ~ ATT + SN + PBC
BEH ~ INT + PBC + INT:PBC
'
# The double-centering approach
est_tpb <- modsem(tpb, TPB)
# Using the LMS approach
est_tpb_lms <- modsem(tpb, TPB, method = "lms")
#> Warning: It is recommended that you have at least 32 nodes for interaction
#> effects between exogenous and endogenous variables in the lms approach 'nodes =
#> 24'
summary(est_tpb_lms)
#>
#> modsem (version 1.0.4):
#> Estimator LMS
#> Optimization method EM-NLMINB
#> Number of observations 2000
#> Number of iterations 103
#> Loglikelihood -23463.37
#> Akaike (AIC) 47034.74
#> Bayesian (BIC) 47337.19
#>
#> Numerical Integration:
#> Points of integration (per dim) 24
#> Dimensions 1
#> Total points of integration 24
#>
#> Fit Measures for H0:
#> Loglikelihood -26393
#> Akaike (AIC) 52892.45
#> Bayesian (BIC) 53189.29
#> Chi-square 66.27
#> Degrees of Freedom (Chi-square) 82
#> P-value (Chi-square) 0.897
#> RMSEA 0.000
#>
#> Comparative fit to H0 (no interaction effect)
#> Loglikelihood change 2929.85
#> Difference test (D) 5859.70
#> Degrees of freedom (D) 1
#> P-value (D) 0.000
#>
#> R-Squared:
#> INT 0.361
#> BEH 0.248
#> R-Squared Null-Model (H0):
#> INT 0.367
#> BEH 0.210
#> R-Squared Change:
#> INT -0.006
#> BEH 0.038
#>
#> Parameter Estimates:
#> Coefficients unstandardized
#> Information expected
#> Standard errors standard
#>
#> Latent Variables:
#> Estimate Std.Error z.value P(>|z|)
#> PBC =~
#> pbc1 1.000
#> pbc2 0.911 0.013 67.91 0.000
#> pbc3 0.802 0.012 65.67 0.000
#> ATT =~
#> att1 1.000
#> att2 0.877 0.012 71.32 0.000
#> att3 0.789 0.012 65.69 0.000
#> att4 0.695 0.011 60.84 0.000
#> att5 0.887 0.013 70.49 0.000
#> SN =~
#> sn1 1.000
#> sn2 0.889 0.017 51.79 0.000
#> INT =~
#> int1 1.000
#> int2 0.913 0.015 59.42 0.000
#> int3 0.807 0.014 55.75 0.000
#> BEH =~
#> b1 1.000
#> b2 0.961 0.030 31.82 0.000
#>
#> Regressions:
#> Estimate Std.Error z.value P(>|z|)
#> INT ~
#> PBC 0.217 0.030 7.29 0.000
#> ATT 0.213 0.026 8.28 0.000
#> SN 0.177 0.028 6.34 0.000
#> BEH ~
#> PBC 0.228 0.023 10.06 0.000
#> INT 0.182 0.025 7.37 0.000
#> PBC:INT 0.204 0.019 10.98 0.000
#>
#> Intercepts:
#> Estimate Std.Error z.value P(>|z|)
#> pbc1 0.959 0.019 50.31 0.000
#> pbc2 0.950 0.018 53.08 0.000
#> pbc3 0.960 0.016 59.11 0.000
#> att1 0.987 0.022 44.10 0.000
#> att2 0.983 0.020 49.45 0.000
#> att3 0.995 0.018 54.27 0.000
#> att4 0.980 0.017 58.41 0.000
#> att5 0.969 0.020 48.14 0.000
#> sn1 0.979 0.023 43.04 0.000
#> sn2 0.987 0.020 48.23 0.000
#> int1 0.995 0.022 46.17 0.000
#> int2 0.995 0.020 49.49 0.000
#> int3 0.990 0.018 53.60 0.000
#> b1 0.989 0.022 45.86 0.000
#> b2 1.008 0.020 50.01 0.000
#> INT 0.000
#> BEH 0.000
#> PBC 0.000
#> ATT 0.000
#> SN 0.000
#>
#> Covariances:
#> Estimate Std.Error z.value P(>|z|)
#> PBC ~~
#> ATT 0.658 0.025 25.84 0.000
#> SN 0.657 0.026 25.04 0.000
#> ATT ~~
#> SN 0.616 0.027 22.54 0.000
#>
#> Variances:
#> Estimate Std.Error z.value P(>|z|)
#> pbc1 0.147 0.008 19.39 0.000
#> pbc2 0.164 0.007 22.22 0.000
#> pbc3 0.154 0.006 24.15 0.000
#> att1 0.167 0.007 23.38 0.000
#> att2 0.150 0.006 24.30 0.000
#> att3 0.159 0.006 26.67 0.000
#> att4 0.163 0.006 27.66 0.000
#> att5 0.159 0.006 24.78 0.000
#> sn1 0.178 0.015 12.12 0.000
#> sn2 0.156 0.012 13.00 0.000
#> int1 0.157 0.009 18.18 0.000
#> int2 0.160 0.008 20.21 0.000
#> int3 0.168 0.007 23.39 0.000
#> b1 0.186 0.019 10.00 0.000
#> b2 0.135 0.017 8.03 0.000
#> PBC 0.933 0.030 31.16 0.000
#> ATT 0.985 0.035 27.94 0.000
#> SN 0.974 0.038 25.45 0.000
#> INT 0.491 0.020 24.40 0.000
#> BEH 0.456 0.022 20.28 0.000Here is an example that includes two quadratic effects and one
interaction effect, using the jordan dataset. The dataset
is a subset of the PISA 2006 dataset.
m2 <- '
ENJ =~ enjoy1 + enjoy2 + enjoy3 + enjoy4 + enjoy5
CAREER =~ career1 + career2 + career3 + career4
SC =~ academic1 + academic2 + academic3 + academic4 + academic5 + academic6
CAREER ~ ENJ + SC + ENJ:ENJ + SC:SC + ENJ:SC
'
est_jordan <- modsem(m2, data = jordan)
est_jordan_qml <- modsem(m2, data = jordan, method = "qml")
summary(est_jordan_qml)
#>
#> modsem (version 1.0.4):
#> Estimator QML
#> Optimization method NLMINB
#> Number of observations 6038
#> Number of iterations 101
#> Loglikelihood -110520.22
#> Akaike (AIC) 221142.45
#> Bayesian (BIC) 221484.44
#>
#> Fit Measures for H0:
#> Loglikelihood -110521
#> Akaike (AIC) 221138.58
#> Bayesian (BIC) 221460.46
#> Chi-square 1016.34
#> Degrees of Freedom (Chi-square) 87
#> P-value (Chi-square) 0.000
#> RMSEA 0.005
#>
#> Comparative fit to H0 (no interaction effect)
#> Loglikelihood change 1.07
#> Difference test (D) 2.13
#> Degrees of freedom (D) 3
#> P-value (D) 0.546
#>
#> R-Squared:
#> CAREER 0.512
#> R-Squared Null-Model (H0):
#> CAREER 0.510
#> R-Squared Change:
#> CAREER 0.002
#>
#> Parameter Estimates:
#> Coefficients unstandardized
#> Information observed
#> Standard errors standard
#>
#> Latent Variables:
#> Estimate Std.Error z.value P(>|z|)
#> ENJ =~
#> enjoy1 1.000
#> enjoy2 1.002 0.020 50.587 0.000
#> enjoy3 0.894 0.020 43.669 0.000
#> enjoy4 0.999 0.021 48.227 0.000
#> enjoy5 1.047 0.021 50.400 0.000
#> SC =~
#> academic1 1.000
#> academic2 1.104 0.028 38.946 0.000
#> academic3 1.235 0.030 41.720 0.000
#> academic4 1.254 0.030 41.828 0.000
#> academic5 1.113 0.029 38.647 0.000
#> academic6 1.198 0.030 40.356 0.000
#> CAREER =~
#> career1 1.000
#> career2 1.040 0.016 65.180 0.000
#> career3 0.952 0.016 57.838 0.000
#> career4 0.818 0.017 48.358 0.000
#>
#> Regressions:
#> Estimate Std.Error z.value P(>|z|)
#> CAREER ~
#> ENJ 0.523 0.020 26.286 0.000
#> SC 0.467 0.023 19.884 0.000
#> ENJ:ENJ 0.026 0.022 1.206 0.228
#> ENJ:SC -0.039 0.046 -0.851 0.395
#> SC:SC -0.002 0.035 -0.058 0.953
#>
#> Intercepts:
#> Estimate Std.Error z.value P(>|z|)
#> enjoy1 0.000 0.013 -0.008 0.994
#> enjoy2 0.000 0.015 0.010 0.992
#> enjoy3 0.000 0.013 -0.023 0.982
#> enjoy4 0.000 0.014 0.008 0.993
#> enjoy5 0.000 0.014 0.025 0.980
#> academic1 0.000 0.016 -0.009 0.993
#> academic2 0.000 0.014 -0.009 0.993
#> academic3 0.000 0.015 -0.028 0.978
#> academic4 0.000 0.016 -0.015 0.988
#> academic5 -0.001 0.014 -0.044 0.965
#> academic6 0.001 0.015 0.048 0.962
#> career1 -0.004 0.017 -0.204 0.838
#> career2 -0.004 0.018 -0.248 0.804
#> career3 -0.004 0.017 -0.214 0.830
#> career4 -0.004 0.016 -0.232 0.816
#> CAREER 0.000
#> ENJ 0.000
#> SC 0.000
#>
#> Covariances:
#> Estimate Std.Error z.value P(>|z|)
#> ENJ ~~
#> SC 0.218 0.009 25.477 0.000
#>
#> Variances:
#> Estimate Std.Error z.value P(>|z|)
#> enjoy1 0.487 0.011 44.335 0.000
#> enjoy2 0.488 0.011 44.406 0.000
#> enjoy3 0.596 0.012 48.233 0.000
#> enjoy4 0.488 0.011 44.561 0.000
#> enjoy5 0.442 0.010 42.470 0.000
#> academic1 0.645 0.013 49.813 0.000
#> academic2 0.566 0.012 47.864 0.000
#> academic3 0.473 0.011 44.319 0.000
#> academic4 0.455 0.010 43.579 0.000
#> academic5 0.565 0.012 47.695 0.000
#> academic6 0.502 0.011 45.434 0.000
#> career1 0.373 0.009 40.392 0.000
#> career2 0.328 0.009 37.019 0.000
#> career3 0.436 0.010 43.272 0.000
#> career4 0.576 0.012 48.372 0.000
#> ENJ 0.500 0.017 29.547 0.000
#> SC 0.338 0.015 23.195 0.000
#> CAREER 0.302 0.010 29.711 0.000Note: Other approaches also work but may be quite
slow depending on the number of interaction effects, particularly for
the LMS and constrained approaches.