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 listens to classic rock at a high volume for 30 minutes, her younger brother listens to classical music quietly 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 is missing from Elaina's scientific investigation?

Constant variables

Explanation:

Elaina's investigation lacked the critical ingredient of constant variables which are important components of every scientific investigation. In every research, there are 3 important variables, namely:

1. Dependent variables: the actual variable to be measured during the course of investigations and whose values are dependent on another variable (independent variable) supplied by the investigators.

2. Independent variable: one of the variables that are supplied by investigators whose values are often manipulated to see the kind of changes it will cause to the dependent variable.

3. Constant variables: other variables that are neither independent nor dependent but constant for all the various experimental groups in investigations.

request for reexamination