However, there actually is strong disagreement between the closed-set NSC results and the delta results. This is because delta-z scores should not be taken seriously unless they are very small (i.e. very negative). Burrows (2003) found that a threshold of 1.9 separated most false positives from true attributions for a set of 17th-century poets. Jockers et al. (2008) failed to do this. In the Jockers et al. (2008) study, only 16 of the 239 chapters had delta-z values as small as 1.9 (Fig. 9). Ten of these 16 chapters were essentially verbatim quotations of Isaiah/Malachi, and all 10 were correctly attributed to Isaiah/Malachi. Four additional chapters were attributed to Isaiah/Malachi and the others to Rigdon and Spalding. The remaining 223 chapters had large delta-z values and were thus apparently false positive. Hence, the delta results of Jockers et al. (2008) actually say little more than what is already uncontroversial about Book of Mormon authorship: that some of the chapters are quotations of Isaiah and Malachi. The delta-z results do not, in fact, attribute sizeable percentages of the chapters to Rigdon, Spalding, or Cowdery.

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We then carried out the extended open-set NSC procedure. Of the 239 Book of Mormon chapters, 175 (73.2%) were classified to one or more unobserved authors, 35 (14.6%) were classified to Isaiah, 17 (7.1%) were classified to early or late Rigdon, 8 (3.4%) were classified to Smith, 2 (0.8%) were classified to Spalding, and 2 (0.8%) were classified to Cowdery (Fig. 11). Seventeen of the 20 Book of Mormon chapters that were essentially verbatim quotations of Isaiah or Malachi were correctly classified. Chapters classified to Rigdon, Smith, or Cowdery appeared to occur essentially at random in the sequence of chapters. The texts classified to Rigdon, Smith, or Cowdery were on the fringe of the Book of Mormon cluster, and the classifications were likely due to multiplicity. Hence, we conclude that based on relative frequencies of the 110 common (mostly non-contextual) words of Jockers et al. (2008), 80% of the non-Isaiah chapters of the Book of Mormon are dissimilar in style from the authors in the candidate set.