Road trauma is the leading cause of death and injury among young people in Australia. The article “The Journey from Traffic Offender to Severe Road Trauma Victim: Destiny or Preventive Opportunity?” (PLoS ONE, April 22, 2015) reported a study to determine factors that might help predict future serious accidents. The article included estimated odds ratios and 95% CIs for true odds ratios for several variables. The response variable here has value y = 1 if a subject was in an accident leading to intensive care admission or death, and 0 otherwise.

a. Which of these four explanatory variables were associated with a decreased likelihood of later severe road trauma? How can you tell?
b. Which of these four explanatory variables were not statistically significant predictors in this model? How can you tell?

c. Interpret the 95% CI provided for e^β₄ .

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x₁ = age/10 x₂ = 1 if male, 0 if female x3 = years with a driver's license X4 = number of prior traffic offenses Est. OR 1.02 1.18 0.99 1.10 OR 95% CI (1.01, 1.03) (0.98, 1.42) (0.98, 0.99) (1.08, 1.11)