An item response theory analysis of safety knowledge in Colorado farm residents

Objective: This study was designed to identify safety knowledge questions that differentiated those with high and low vulnerability to injury and assess differences in safety questions by sex and age. Methods: Colorado farm operators and their spouses were recruited in 1993 from farm truck registrations (n = 872) and between 1993 and 1997 from property value assessment lists or rural directories (n = 761). Item Response Theory was used to assess ten safety questions. Results: Knowing fatigue causes injury best discriminated between high and low injury vulnerability; incorrectly answering the question about inattention causing injury was associated with highest vulnerability to injury. No measurement invariance was identified by sex, but those older than 65 years answered differently than those younger than 45 years (P = 0.005). Conclusion: Safety programs emphasizing the role of fatigue and inattention on injury risk might reduce injuries in the farming community.