A personal trainer thinks her clients get better workouts and are stronger if they listen to music while working out. Over the next week, she divides her 20 clients into two groups of 10. For the first group, she plays music and sees if they can lift a barbell weighing 50 lbs. For the second group, she repeats the test but does not play any music. All 10 members of the music group could lift the barbell, but only 7 members of the no music group could lift the barbell. She concludes that her hypothesis was correct and decides to always play music for her clients. What was the personal trainer’s hypothesis?