Determining the number of factors to extract is a critical decision in exploratory factor analysis. Simulation studies have found the Parallel Analysis criterion to be accurate, but it is computationally intensive. Two freeware programs that implement Parallel Analysis on Macintosh and Windows operating systems are presented.
Watkins, Marley W.
"Determining Parallel Analysis Criteria,"
Journal of Modern Applied Statistical Methods: Vol. 5
, Article 8.
Available at: http://digitalcommons.wayne.edu/jmasm/vol5/iss2/8