Efficient methods of using the Statistical Package for the Social Sciences (SPSS) to analyze National Assessment of Educational Progress (NAEP) data files are discussed. One error in the NAEP SPSS file is discussed, and another error (which may be system-dependent) is mentioned. In addition, purely mathematical methods are used to address the questions of whether there is evidence for the existence of four hypothesized traits (Words and Phrases, Lexical Relationships, Propositional Relationships, and Textual Relationships). Further, the question of estimating reliability of a new set of items gathered from different NAEP booklets is addressed. It is concluded that the current data do not support the thesis that these traits are distinct, although there is some evidence that Words& Phrases and Lexical Relationships are distinct. It is further concluded that the reliability of new sets of items cannot be safely estimated at this time. (Author)