Based on past results found in the Information Please Almanac, there is a 0.120 probability that a baseball World Series contest will last four games, a 0.253 probability that it will last five games, a 0.217 probability that it will last six games, and a 0.410 probability that it will last seven games. Find the mean and standard deviation for the numbers of games that World Series contests last. Is it unusual for a team to "sweep" by winning in four games?