Suppose that our golf ball experiment calls for nine trials, but the player that we are using hurts his wrist. Luckily, Bubba Watson is practicing on the same range and graciously agrees to participate in our experiment. His club-head speed is 120 miles per hour and he hits the golf ball 305 yards. Is Bubba’s shot an influential observation?

The least-squares regression line without Bubba is ŷ = 3.1661 x - 55.7966.

Approach Recompute the least-squares regression line with Bubba included. If the slope or y-intercept of the least-squares regression line changes substantially, Bubba’s shot is influential.