In 2010, Josh Johnson of the Florida Marlins had the lowest earned-run average (ERA is the mean number of runs yielded per nine innings pitched) of any starting pitcher in the National League, with an ERA of 2.30. Also in 2010, Felix Hernandez of the Seattle Mariners had the lowest ERA of any starting pitcher in the American League with an ERA of 2.27. In the National League, the mean ERA in 2010 was 3.622 and the standard deviation was 0.743. In the American League, the mean ERA in 2010 was 3.929 and the standard deviation was 0.775. Which player had the better year relative to his peers, Johnson or Hernandez? Why?