Reliability and validity of a combat exposure index for vietnam era verterans

The reliability and validity of a self‐report measure of combat exposure are examined in a cohort of male‐male twin pairs who served in the military during the Vietnam era. Test‐retest reliability for a five‐level ordinal index of combat exposure is assessed by use of 192 duplicate sets of responses. The chance‐corrected proportion in agreement (as measured by the kappa coefficient) is 0.84. As a measure of criterion‐related validity, the combat index is correlated with the award of combat‐related military medals ascertained from the military records. The probability of receiving a Purple Heart, Bronze Star, Commendation Medal and Combat Infantry Badge is associated strongly with the combat exposure index. These results show that this simple index is a reliable and valid measure of combat exposure.