After researching the possible effects of music, Elaina proposes that if people listen to faster-paced music, their pulse rates will increase more than if they listen to slower music. Her mother quietly listens to classic rock at a high volume for 30 minutes, her younger brother listens to classical music
while he sleeps at night, and her grandmother listens to two hours of rap at a medium volume. Elaina records each person's pulse before and after
listening to the music.
What can you infer is missing from Elaina's scientific investigation?
O Atestable hypothesis naming independent and dependent variables
O An experiment that takes initial and final measurements
O Controlled variables with only one varied independent variable
O Experimental data that can be recorded and analyzed