The common item in measurement: Effects on structure

Procedures for analyzing common item effects on the inference of personality structure were reviewed and a study using smallest space analysis of the CPI reported. Solutions to three matrices—intercorrelation matrix of the original CPI scales, of reduced scales (with common items removed), and of the number of common items—were compared visually, and by inter-point distance correlations and configurational similarity analyses. Marked similarity among the original structure, the item-overlap-free structure and the built-in structure was observed. It was concluded that common items magnify an intrinsic structure already existing among scales and that the common-item problem is not likely a serious one in personality measurement.