15 “occur together” symptoms and the 15 “ever occur” symptoms, respectively. The variability and heritability of these two sets of principal dimensions were compared to select between the two sets of variables. MCA was then applied to all of the 69 selected variables to reduce the data dimension. The number of dimensions retained was guided by the Benzécri adjusted cumulative percentage, showing the percentage of variance explained by the retained dimensions (Benzécri, 1992).
