General guides include, Tabachnick's rule of thumb10 that suggests having at least 300 cases are needed for factor analysis. Hair et al9 suggested that sample sizes should be 100 or greater. A number of textbooks1,8-10 cite the work of Comrey and Lee13 in their guide to sample sizes: 100 as poor, 200 as fair, 300 as good, 500 as very good, and 1000 or more as excellent.