123 Point spreads of NFL games. During the National Football League (NFL) season, Las Vegas oddsmakers establish a point spread on each game for betting purposes. For example, the Champion Green Bay Packers were established as 2.5-point favorites over the Pittsburgh Steelers in the 2011 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 outcome of the game and the point spread (called a point-spread error) was calculated for 240 NFL games.

The mean and standard deviation of the point-spread errors are x = -1.6 and s = 13.3. Suppose the researcher wants to know whether the true standard deviation of the point-spread errors exceeds 15. Conduct the analysis using a = .05.