John studied the motion of a pendulum. He used the same length of pendulum string, but two different masses. He measured the period of the pendulum with the same angle of displacement. In 100 trials, regardless of the mass, the period was the same, 1 percent. John concluded that the period of a pendulum swing is not dependent on the mass.
In the scenario described, how did John determine his conclusion about the period of the pendulum's motion?
deductive reasoning from a valid principle
deductive reasoning from an invalid principle