# 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