Correlation Strength:

• 0.7 to 1.0: Strong positive
• 0.3 to 0.7: Moderate positive
• -0.3 to 0.3: Weak
• -0.7 to -0.3: Moderate negative
• -1.0 to -0.7: Strong negative

Correlation Methods:

• Pearson: Linear relationships
• Spearman: Monotonic relationships
• Kendall: Ordinal data

Interpretation:

• Positive: Variables increase together
• Negative: One increases, other decreases
• Correlation ≠ Causation