Which statement about correlation is true?

• A. The relationship between variables, which can be positive or negative
• B. It indicates a causal relationship
• C. It measures the magnitude of risk directly
• D. It is always independent of the study design

Answer: (C)

Correlation describes how two variables relate to each other, specifically whether they move together and how strongly. The key part is that the relationship can be positive (both tend to increase together) or negative (one tends to increase while the other decreases). It does not tell you that one variable causes the other to change, and it does not quantify the magnitude of risk directly—risk is measured with different metrics like relative risk or odds ratio. Observed correlation can also be influenced by study design, sampling, measurement error, and confounding, so it’s not entirely independent of how a study is conducted. Therefore, the true statement is that the relationship between variables can be positive or negative.