Inference about Two Proportions 1) A study was made of 500 children who were hospitalized as a result of motor vehicle crashes. Among 310 children who were not using seat belts, 70 were injured severely. Among 190 children using seat belts, 20 were injured severely. Is there sufficient sample evidence to conclude, at the 0.05 significance level, that the proportion of severe injuries is lower for children wearing seat belts?