During the National Football League (NFL) season, Las Vegas oddsmakers establish a point spread on each game for betting purposes. For example, the St. Louis Rams were established as 7-point favorites over the Tennessee Titans in the 2000 Super Bowl. The final scores of NFL games were compared against the final point spreads established by the oddsmakers in Chance (Fall 1998).The difference between the game outcome and point spread

(called a point-spread error) was calculated for 240 NFL games. The mean and standard deviation of the pointspread errors are y = -1.6 and s = 13.3. Use this information to test the hypothesis that the true mean point-spread error for all NFL games is 0. Conduct the test at a! = .O1 and interpret the result.