Independent vs. Dependent (pick one)

Question

• On average, do women perform better on their statistics
final than men?
• On average, is there a difference in people’s blood
pressure before and after giving a speech. 40 people’s blood
pressure was measured before and after giving a public
speech.
• At a specific restaurant, is the average tip percent greater
for supper than lunch? 35 wait staff who worked both lunch
and supper check their receipts and tips.
• On average, are Americans more stressed compared to the
French? 50 people from each country were given a stress
test.

Answer 1

I'll pick the second option: "On average, is there a difference in people’s blood pressure before and after giving a speech?"

In this case, the independent variable is whether the blood pressure measurement is taken "before" or "after" giving a speech. This is an experimental condition that is being manipulated.

The dependent variable is the blood pressure measurement itself, as it is the outcome being measured to see if there is any effect due to the independent variable (the timing of the measurement).

This situation represents a paired sample comparison (dependent samples) because the same individuals' blood pressure is measured at two different times (before and after the speech).