Lecture 17 - Exploratory Factor Analysis Theory Flashcards
What is a latent variable?
A variable which cannot be measured directly but that has aspects which may be measured
E.g. You can’t measure cognitive function directly, but you can measure things such as word comprehension and spatial imagination
What does EFA stand for
Exploratory factor analysis
What does EFA aim to do
To understand the structure of a set of variables
To reduce a large set of variables to a smaller set of variables, without losing information
To explain correlations between variables in terms of common factors and cross loadings
What is the R-Matrix in EFA and what does it do?
It is a table showing correlations between variables
1 means each variable is completely correlated with itself, of course
What does a scree plot show?
Eigenvalue vs factor
Helps us decide how many factors to use in EFA
What is the K1 rule in EFA
Using all factors with an eigenvalue greater than 1
What is the scree test (Catell) in EFA
The cutoff point for what factors to use is the point of inflection
So one line comes at a different angle to the other, and this has something to do with it
What is the parallel analysis (Horn) approach to deciding factors in EFA
Compare eigenvalues to randomly produced ones. Use those factors that have eigenvalues bigger than the random produced eigenvalues
How do we graphically represent factors in EFA
A graph from -1 to +1 on both axis, meeting in the middle like a +. These two axis represent factors
Then we plot the variables onto this graph
What’s a problem with graphically representing factors in EFA
Loadings are highest on the first factor so interpretation is difficult
Why do we do rotation in EFA
We rotate the axis to maximise the loading of a cluster onto one factor
What are the three types of rotation in EFA?
Orthogonal (varimax)
Oblique (direct oblimin)
Parameter (o with a weird devil tail coming out of it)
What is the absolute minimum number of participants needed for EFA
100
What does communality mean?
The proportion of variance that is common to each variable
What does RIT stand for?
Recaptured item technique
