Correlation is a statistical measure that shows the relationship between two variables — how one variable changes when the other changes. It tells you whether two variables tend to increase together, decrease together, or have no clear pattern.

Key points:

• Ranges from –1 to +1:

  • +1 = perfect positive relationship (as one increases, the other increases),

  • –1 = perfect negative relationship (as one increases, the other decreases),

  • 0 = no linear relationship.

• It does not prove cause and effect — just association.