In a car crash experiment, cars are classified into one of four groups: subcompact, compact, midsize, and full-size. There are five different cars in each group. Head injury data (in hic, which are standard head injury condition units) for the dummies in the driver's seat are listed in the accompanying table. Use a 0.05 significance level. Test the null hypothesis that the different weight categories have the same mean. Do the sample data suggest that larger cars are safer?