Maimaris, Summer, Browning, and Palmer (1994) reported on a study of head injuries in children and adults involved in bicycle accidents. They broke down the data on the basis of Age, whether a motor vehicle was involved, whether the rider was wearing a helmet, and whether there was a head injury. The data appear below.

Motor Vehicle Helmet Injury Count Young Yes Yes Yes 0 No 9 No Yes 8 No 36 No Yes Yes 0 No 41