Final answer:
The independent variable is the amount of medication taken in the morning.
Step-by-step explanation:
The independent variable in this scenario is the amount of medication taken in the morning. An independent variable is the variable that is changed or manipulated by the researcher to see its effect on the dependent variable. In this case, the researcher is altering the dosage of the medication to observe its impact on the amount of sleep that night.
Learn more about Impact of medication on sleep