Lab partner Vera and Bill Confuzzens attempted to use Trials 5 and 8 to show the affect that a?

Lab partner Vera and Bill Confuzzens attempted to use Trials 5 and 8 to show the affect that a doubling of force has upon the acceleration. Why these two trials cannot be used to show the affect of force upon acceleration?

Trial 5: Applied Force: 80.0 N Mass: 2.0 kg Net Force: 80.0 N Velocity-time Information: 3.0s, 120.0 m/s Acceleration: 40.0 m/s^2

Trial 8: Applied Force: 40.0 N Mass: 3.0 kg Net Force: 40.0 N Velocity-time information: 3.0s, 40.0 m/s Acceleration: 13.33 m/s^2