Scree plot
Plots the eigenvalues of the correlation matrix in decreasing order, to help decide how many factors or components to keep.
Menu: Graphs → More charts → Scree plot…
When should I use it?
- Before or after a factor analysis or PCA.
What are the assumptions?
- Three or more scale variables (listwise complete cases).
How do I run it in StatLab?
- Choose the variables.
How do I read the output?
| Output | Meaning |
|---|---|
| Eigenvalues | Keep the components before the “elbow”; the dashed line marks eigenvalue 1 (Kaiser). |
Worked example
On the practice survey dataset (File → Sample dataset), this command — which the dialog's Paste button also produces — runs the procedure:
PROC vizScree /vars=(score age pre).
Computed by StatLab's validated procedure code when this page was built. The example only illustrates the steps; choose variables that fit your own research question.
What are common mistakes?
- Using the Kaiser rule alone — combine it with the elbow and interpretability.