Stat 5600 — Applied Multivariate Statistics
Homework 6
Confirmatory Factor Analysis
Due 5:00 Friday, March 9
1. Recall, the PSYCH TESTS dataset from homework 5 is a triangular correlation ma-
trix for nine psychological/intelligence tests on 145 children. Use read.tri to import
this matrix and use the sem package to run a confirmatory factor analysis on the
PSYCH TESTS data to answer question 6.9.
2. Import the COGNITION dataset from the website and remove the observations with
missing values, as in homework 4. Use Table 4.1 to identify the variables which are
reverse-coded, and multiply those columns by -1, so that all variables are measured
in the same direction. For example, to reverse item 3, use something like
cog[,3] <- -1*cog[,3] .
Use this modified data set and sem to answer question 6.8. (The modification is
necessary for part b. The sem function can fix loadings to be equal, but not to be
equal in absolute value but with different signs.)
