**Core Concept:** The correlation coefficient (r) is a statistical measure used to assess the strength and direction of the linear relationship between two continuous variables. A value of -1 indicates a perfect negative correlation, 0 indicates no correlation, and 1 indicates a perfect positive correlation.

**Why the Correct Answer is Right:** The correlation coefficient (r) ranges from -1 to 1. This means that r can take on values between -1 and 1, inclusive. A value of -1 indicates a perfect negative correlation, meaning that as one variable increases, the other decreases; 0 indicates no correlation, suggesting that the variables are unrelated; and 1 indicates a perfect positive correlation, meaning that as one variable increases, the other also increases.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because a value of -1 would imply a perfect negative correlation, which is the correct answer choice (B).
B. This option is incorrect because a value of 0 indicates no correlation, not a range of values between -1 and 1.
C. This option is incorrect because a value of 1 would imply a perfect positive correlation, while the correct answer shows a range between -1 and 1.
D. This option is incorrect because a value of 0.5 indicates moderate correlation, not a range of values between -1 and 1.

**Clinical Pearl:** While correlation does not imply causation, understanding correlation coefficients can help physicians evaluate the strength and direction of relationships between variables in clinical research and practice, informing decision-making and hypothesis generation.