| The history of code type interpretation of the MMPI (Hathaway & McKinley, 1942) and MMPI-2 (Butcher, Dahlstrom, Graham, Tellegen, and Kaemmer, 1989) is reviewed. Four MMPI-2 outpatient code types reported by Graham, Ben-Porath, and McNulty (1999) and four inpatient code types reported by Arbisi, Ben-Porath, and McNulty (2000) were investigated for incremental validity. Regression analyses generally failed to support incremental validity for well-defined (those with 5 T-score points between the 2nd and 3rd highest scales) outpatient code types using unique and inclusive correlates as dependent variables. Modest support for incremental validity was found for the 13/31 well-defined outpatient code type for somatization indicators. Results were similar for inpatient well-defined code types with largely negative findings. Results for ill-defined outpatient and inpatient code types also generally failed to support incremental validity. Some ill-defined code types demonstrated incremental validity, but these code types generally had numerous secondary elevations that may have contributed to the significant results. Clinicians may be able to obtain equivalent information from MMPI-2 single scale interpretation without the complexity of two-point code type classification. |
