Description Usage Arguments Details Value Author(s) References See Also Examples
mod.indices
calculates modification indices (score tests)
and estimated parameter changes for the fixed and constrained
parameters in a structural equation model. [Warning: This is a
preliminary version: the computed values are a bit off the correct
values.]
1 2 3 4 5 6 7 8 9 10 11 | mod.indices(model, ...)
## S3 method for class 'sem'
mod.indices(model, ...)
## S3 method for class 'sem.modind'
print(x, n.largest=5, ...)
## S3 method for class 'sem.modind'
summary(object, round=2,
print.matrices=c("both", "par.change", "mod.indices"), ...)
|
model |
an object of class |
object, x |
an object of class |
n.largest |
number of modification indices to print in each of the A and P matrices of the RAM model. |
round |
number of places to the right of the decimal point in printing modification indices. |
print.matrices |
which matrices to print: estimated changes in the fixed parameters, modification indices, or both (the default). |
... |
arguments to be passed down. |
Modification indices are one-df chi-square score statistics for the fixed and constrained
parameters in a structural equation model. They may be regarded as an estimate of the improvement
in the likelihood-ratio chi-square statistic for the model if the corresponding parameter is
respecified as a free parameter. The mod.indices
function also estimates the change in the
value of a fixed or constrained parameter if the parameter is respecified as free. When several
parameters are set equal, modification indices and estimated changes are given for all but the first.
Modification indices and estimated parameter changes for currently free parameters are given as
NA
.
The method employed is described in Saris, Satorra, and Sorbom (1987) and Sorbom (1989).
mod.indices
returns an object of class sem.modind
with the following elements:
mod.A |
modification indices for the elements of the A matrix. |
mod.P |
modification indices for the elements of the P matrix. |
par.A |
estimated parameter changes for the elements of the A matrix. |
par.P |
estimated parameter changes for the elements of the P matrix. |
John Fox jfox@mcmaster.ca
Sarris, W. E., Satorra, A., and Sorbom, D. (1987) The detection and correction of specification errors in structural equation models. Pp. 105–129 in Clogg, C. C. (ed.), Sociological Methodology 1987. American Sociological Association.
Sorbom, D. (1989) Model modification. Psychometrika 54, 371–384.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 | ## Not run:
# This example is adapted from the SAS manual
S.wh <- read.moments(names=c('Anomia67','Powerless67','Anomia71',
'Powerless71','Education','SEI'))
11.834
6.947 9.364
6.819 5.091 12.532
4.783 5.028 7.495 9.986
-3.839 -3.889 -3.841 -3.625 9.610
-21.899 -18.831 -21.748 -18.775 35.522 450.288
model.wh <- specify.model()
Alienation67 -> Anomia67, NA, 1
Alienation67 -> Powerless67, NA, 0.833
Alienation71 -> Anomia71, NA, 1
Alienation71 -> Powerless71, NA, 0.833
SES -> Education, NA, 1
SES -> SEI, lamb, NA
SES -> Alienation67, gam1, NA
Alienation67 -> Alienation71, beta, NA
SES -> Alienation71, gam2, NA
Anomia67 <-> Anomia67, the1, NA
Anomia71 <-> Anomia71, the1, NA
Powerless67 <-> Powerless67, the2, NA
Powerless71 <-> Powerless71, the2, NA
Education <-> Education, the3, NA
SEI <-> SEI, the4, NA
Anomia67 <-> Anomia71, the5, NA
Powerless67 <-> Powerless71, the5, NA
Alienation67 <-> Alienation67, psi1, NA
Alienation71 <-> Alienation71, psi2, NA
SES <-> SES, phi, NA
sem.wh <- sem(model.wh, S.wh, 932)
mod.indices(sem.wh)
## 5 largest modification indices, A matrix:
## Powerless67:Education Anomia67:Education
## 4.8736 3.8027
## Powerless67:SES Education:Powerless67
## 2.7608 2.4619
## Anomia67:SES
## 2.3122
##
## 5 largest modification indices, P matrix:
## Education:Powerless67 Education:Anomia67
## 6.4028 4.5398
## SES:Powerless67 SES:Anomia67
## 2.7608 2.3122
## SEI:Powerless67
## 1.3185
## End(Not run)
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