1. The problem asks us to interpret a correlation coefficient of $-0.85$ between two data sets. 2. The correlation coefficient, denoted as $r$, measures the strength and direction of a linear relationship between two variables. 3. The value of $r$ ranges from $-1$ to $1$. 4. A value close to $-1$ indicates a strong negative linear relationship, meaning as one variable increases, the other tends to decrease. 5. A value close to $1$ indicates a strong positive linear relationship, meaning both variables increase together. 6. A value near $0$ indicates little to no linear relationship. 7. Since $-0.85$ is close to $-1$, it indicates a strong negative correlation. 8. Therefore, the best description is that the two data sets have a strong inverse linear relationship: when one increases, the other tends to decrease significantly.