Factor analysis Flashcards
-Understand what a thematic analysis is and what it is for -Understand how to read the SPSS outputs and what sig values for what section!
what is factor analysis for
- A method to assess the extent to which a
questionnaire is measuring a latent variable. - It explores correlation patterns between items to
establish an underlying structure.
‒ Think of a factor as a ‘subscale’ - A data reduction method
what SPSS OUTputs do we need to look at
. the correlation matrix
. the KMO and Barletts test of sphericity (Factorability of the data)
. table of communalities
. total variance explained table
. scree plot
. pattern matrix
The correlation matrix
All items must correlate (above ..30) with at least ONE other item
None should correlate above .80 with eachother as this would be multicollinearity/singularity (too similar)
Factorability of the data
KMO- accept anything above .5 or .6 (suitability for factor analysis). Write KMO=
Barlett’s test of sphericity= p<.05
x2= chi2 (df), p< sig.
e.g. x2= 555.6 (75)=, p<0.01
suitability for factor analysis
Communalities table
All extraction numbers must ne above .40
>.40
get rid if there is
total variance explained table
Shows us how many factors have been extracted-
there specific eigenvalues are under ‘total’
WHEN ASKED- ‘how much of the total varience does the proposed factor structure explain’- look at the cumulative % and take the last number of the last factor excluded (this is the total)
scree plot
Look for devees in the L
this should match the total number of factors excluded
should be an L
The pattern matrix
Does each item have a factor it loads on to?
To load it must be above .40
are there any cross loading- does one item load onto more than one factor?
UNSTABLE FACTORS- if a factor has less than 3 items, this is unstable and we should consider removing
- What does the table of communalities tell us
It tells us how much variance in each item is explained by the proposed factor structure. The extracted values can be treated as percentages. Values below .40 are a problem, and it may be worth removing these items.
