Abel and Kruger (2010) recently analyzed the smiles of professional baseball players listed in the Baseball Register. The photos of players were classified as either big smiles or no smiles. The age of death for all players was also recorded. The results revealed that players with big smiles lived longer than those with no smiles. Which statistic could be used to determine if the difference in life span between those with big versus no smiles was greater than would be expected by sampling error? [More-recent research has not replicated this finding.]