With out a ratio of aluminum to wooden bats involved in the 2 out of 3 deaths being caused by wooden bats, one cannot draw any kind of conclusion. It could mean that aluminum bats are way more dangerous if 1/10 of the bats being used in the study were aluminum. Or it could mean that wooden bats are more dangerous if 1/10 of the bats were wooden.
IF the amount of wooden bats were exactly double that of aluminum they would both be equally dangerous. If the number of aluminum bats being used were more than half the number of wooden bats bats then the aluminum bats would be more dangerous.