How did people get from place to place during the 1920s?

In the 1920's, trains and ocean liners were the dominant mass transportation methods, providing comfortable, reliable transport to millions of American vacationers. Trains had opened up the continent and ships the world, but newer methods of transport captured the imagination of the public and reduced travel times.

Explanation:

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.