Answer and Explanations:
An Independent variable is a variable that can be controlled by the experimenter. The dependent variable depends on other variables (particularly on the independent variable)
Considering the given scenarios one after the other:
Sleep quality = Dependent variable
This is because it is an output variable depending on the screen time before bed
The number of siblings = Independent variable
It is an independent variable because it is an input variable on which the allowance of the people depends.
The final grade = Dependent variable
It is a dependent variable because it is an output variable that depends on the typing speeds of the students
The amount of vitamin D the kids take = independent variable
This is because it is an input variable on which the number of ear infections (output) depends
Size of tomatoes = Dependent variable
It is a dependent variable because it depends on the level of sunlight.