Article Text

Using the unmatched count technique to improve base rate estimates of risky driving behaviours among veterans of the wars in Iraq and Afghanistan
  1. Sean C Sheppard1,2,
  2. Mitch Earleywine1
  1. 1Department of Psychology, The University at Albany, State University of New York, Albany, New York, USA
  2. 2National Center for Veterans Studies, University of Utah, Salt Lake City, Utah, USA
  1. Correspondence to Dr Sean C Sheppard, National Center for Veterans Studies, University of Utah, 260 S. Central Campus Dr., Room 205, Salt Lake City, UT 84112, USA; sheppard73b{at}


Background Few studies have investigated base rate estimates of risky driving behaviours among veterans of the wars in Afghanistan and Iraq despite evidence suggesting such behaviours result in increased death rates. In addition, published estimates of driving behaviours may be subject to a significant response bias via the impact of perceived mental health stigma on honest self-reporting.

Aim The present study compared the unmatched count technique, a form of randomised response technique used to mitigate biased responding, with traditional anonymous self-report to gain information about base rates of risky driving behaviours among combat veterans.

Methods Cross-sectional data gathered as part of a study of attitudes and behaviours related to military service provided estimates of target activities. Six facets of risky driving (horn honking, carrying firearms in the vehicle, drinking and driving, screaming at other drivers, following other drivers to complain, and tailgating) were assessed.

Results In our sample of 1351 combat veterans, the unmatched count technique revealed significantly higher rates relative to traditional anonymous assessment specifically for horn honking in anger (22.1% vs 13.6%), carrying firearms (51.1% vs 32.2%), and drinking and driving (77.8% vs 54.0%). There were no significant differences for the remaining three items.

Conclusions The high level of morbidity associated with risky driving and motor vehicle crashes is a significant concern in the combat veteran population. These data suggest the presence of a strong response bias associated with endorsing certain risky driving behaviours, potentially leading to serious underestimation of these problem behaviours in standard anonymous questionnaires.

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