then administered to 449 clinical and non-clinical participants. The number of items was reduced based on a rational approach according to the degree to which they fit Millon's evolutionary theory. Items were also eliminated based on simplicity, grammar, content, and scale relevance. Internal-structural validity Once the initial item pool was reduced after piloting, the second validation stage assessed how well items interrelated, and the psychometric properties of the test were determined. 106 items were retained and administered along with the 175 MCMI-III items. The ability of the MCMI items to give reliable indications of the domains of interest were examined using internal consistency and test-retest reliability. Internal consistency is the extent to which the items on a scale generally measure the same thing. Cronbach’s alpha values (an estimate of internal consistency) median (average) values were 0.84 for the personality pattern scales, 0.83 for the clinical syndrome scales, and 0.80 for the Grossman Facet Scales. Test-retest reliability is an estimate of the stability of the responses in the same person over a brief period of time. Examining test-retest reliability requires administering the items from the MCMI-IV at two different time periods. The median testing interval between administrations was 13 days. The higher the correlation between scores at two time points, more stable the measure is. Based on 129 participants, the test-retest reliability of the MCMI-IV personality and clinical syndrome scales ranged from 0.73 (Delusional) to 0.93 (Histrionic) with a most values above 0.80. These statistics indicate that the measure is highly stable over a short period of time; however, no long-term data are available. After examining the psychometrics of these "tryout" items, 50 items were replaced, resulting in 284 items that were administered to the standardization sample of 1,547 clinical patients. External-criterion validity The final validation stage included examining convergent and discriminative validity of the test, which is assessed by correlating the test with similar/dissimilar instruments. Most correlations between the MCMI-IV Personality Pattern scales and the MMPI-2-RF (another widely used and validated measure of personality psychopathology) Restructured Clinical scales were low to moderate. Some, but not all, of the MCMI-IV Clinical Syndrome scales were correlated moderately to highly with the MMPI-2-RF Restructured Clinical and Specific Problem scales. The authors describe these relationships as "support for the measurement of similar constructs" across measures and that the validity correlations are consistent with the "argument that the two assessments are best used complimentarily to