Week 4 Flashcards
Partial Correlation
- Useful to detect spuriousness
- Needed to understand
- Factor Anlysis
- Multiple regression
- ANCOVA
- introduces Venn diagriams
Factor Analysis
- A set of statistical procedures
- Determines the number of distinct unobservable constructs needed to account for the pattern of correlations among a set of measures
Correlation in SPSS
- r(N-1) = CCA, p<.001
- In this instance coefficient equals .35
- This is greater than .001
- Therefore is significant
Bivariate (Zero Order) Correlation (R)
- used to determine the existence of relationships between two different variables
- Can be represented with Venn Diagrams
Partial Correlation (PR)
- Describe the relationship between two variables whilst taking away the effects of another variable, or several other variables, on this relationship.
Spurious Correlation
- Connection between two variables that appears to be causal but is not.
Venn Diagrams
Overlapping circles or other shapes to illustrate the logical relationships between two or more sets of items.
Exploratory Factor Analysis
- Data Reduction Technique
- Reveals underlying structure of intercorrelations
- How scale items cluster together
The goal is to summarise the relationships between variables by creating sub-sets of variables
Subsets are known as Factors - Constructs cannot be observed but are inferred by correlations
Correlation Matrix
a symmetrical square that shows the degree of association between all possible pairs of variables contained in a set.
Latent Variables
- These are our constructs or factors and cannot be observed
- Can be observed by the way they affect on observable variables
Manifest Variables
- can be directly observed or measured such as behaviour
- does not need to be inferred
- Used to study latent variables.
- Correlations between them create super-variables or constructs
What is Factor Analysis Used For?
- Scale Development
- Scale Checking and Refining
- Data Reduction
Factor Analysis Uses - Scale Development
- Count how many sub-scales we have
- Which items belong to sub-scales
- Which items should be discarded
Factor Analysis Uses - Scale Checking and Refining
- When used in research does the factor replicate like any previous research?
- Factors are not fixed to any scale: Big Five with University Students vs Nursing Home Residents
- Should I make any changes
- Should be conducted and reported when existing scale is used in research
- Ensure factors are apporpriate for the context
Factor Analysis Uses - Data Reduction
- To create new Factor Scores
- Can be used as predictors or new outcome variables
- We don’t tend to use this very often
Determinant
- Individual characteristics, such as cognitions, beliefs and motivation, that could potentially be associated with Constructs
- A determinant > .00001 suggests that multicollinearity is not a problem
Multicollinearity
- Very high correlation between variables
- If correlations are all small there is no point of running a factor analysis
Self Efficacy Scale
- 10-item self-report measure of global self-esteem
- Rosenberg rated with 5-point scale strongly agree to strongly disagree
Factor Analysis - Preliminary Checks 1 & 2
- Look for patterns of correlations between variables
- No point continuing if variables are not correlated
- If correlations are low then we could end up with as many factors as items
Zero Order Correlation Matrix
- Correlation between two variables without influence of any other variables.
- Same thing as a Pearson correlation.
A Determinant
- Determinant > .00001 suggests that multicollinearity is not a problem.
Factor Analysis
- Interpret a factor of a measure
- Uses the correlation of observed variables to estimate latent variables known as factors
- Look for patterns of correlations between variables
- Use factor analysis to identify the hidden variables.
Asking in Factor Analysis
- Asking if intercorrelations amongst items support separate constructs
- How many constructs do we really need to summarise the items
- Which items belong to each construct
- There is no point in continuing if the variables are not correlated
Zero Order Correlation Matrix
- Looks at correlations between each pair of variables without considering the influence of any other variables
- Don’t run factor analysis if correlations are small this results in too many factors
- Too much correlation indicates multicollinearity