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. Author manuscript; available in PMC: 2014 Dec 1.
Published in final edited form as: J Pain. 2013 Dec;14(12 0):10.1016/j.jpain.2013.07.018. doi: 10.1016/j.jpain.2013.07.018

Figure 1. Scree plot and parallel analysis from exploratory factor analysis (EFA).

Figure 1

The vertical lines depict the eigenvalues for each factor, showing a turn at factor 3. The solid line depicts the upper bound of the 95% confidence interval for eigenvalues that would be expected for each factor from an EFA computed on a random dataset of the same size as the actual data. As can be seen, the observed eigenvalues for the first 3 factors exceed the chance line, consistent with the scree plot interpretation.