Answer:
4. The amount of caffeine in the drinks
5. The heart rate of the participants of the experiments
6. Water
7. i) The volume of drink taken should be constant
ii) The frequency of taking their drink is constant
iii) The time of drinking by the brothers is constant
Explanation:
In the question, Jeffery intends to find the caffeine drink that will result in the heart rate increasing most
The variables (varieties) of drinks tested by Jeffery = Pepsi, espresso, and water
Drink variable arranged by the order of increasing Caffeine content are presented as follows;
Caffeine content of water < Caffeine content of Pepsi < Caffeine content of espresso
The triplet with the double shot of espresso = The triplet with the highest heart rate
4. The independent variable is the variable which is suspected to be the cause of the specified observation
Therefore, in the question, the independent variable are the drinks with different amount of caffeine
5. The dependent variable is the effect or the outcome of the independent variable
The dependent variable in the question is the heart rate of the subjects in the study
6. The control group is the independent variable or input that is expected to give the minimum effect or output compared to other independent variables in the study such that the control group does not contain the suspected cause of the observation or effect under investigation
The control group (or variable) in the question is water which does not contain caffeine
7. Three constants that all three brothers should be doing are;
i) The three brothers should be taking a constant or the same quantity of their preferred drink
ii) The frequency at which they take their drinks should be constant
iii) The time at which the brothers take the drink should be the same
