Sheeba is trying to determine how muisc affects a person's pulse rate. she has her mother listen to classic rock at a high volume for 30 minutes, her younger brother listen to classical muisc quietly while he sleeps at night, and her grandmother listen to 2 hours of rap at a medium volume. she records each person's pulse before and after listening to the muisc. what is missing from sheeba's scientific investigation? (1 point)

test subjects willing to participate in the experiment

a specific hypothesis to test with a controlled experiment

experimental data that can be recorded and analyzed

an experiment that takes initial and final measurements