Practice problem

Scatter Plots: Correlation vs. Causation

A confounding variable (also called third variable) can interfere with the relationship between the independent and dependent variables.

A classic example of a confounding variable is the correlation between murder rates and ice cream sales throughout the year. While murder and ice cream are clearly unrelated, there is a variable that relates to both of them: seasons. It turns out that both murder rates and ice cream sales increase in the summer due to the increased temperatures.

Suppose we have an independent variable $IV$ , a dependent variable $DV$ , and a confounding variable $CV$ . Assuming we see a correlation within the scatter plot of $DV$ and $IV$ , which of the following statements are true?