What does correlation in statistics measure?

Correlation in statistics specifically measures the relationship between two variables. This relationship can indicate whether changes in one variable are associated with changes in another variable. Correlation is quantified using a correlation coefficient, which indicates not only the strength but also the direction of the relationship. A positive correlation means that as one variable increases, the other tends to increase as well, while a negative correlation indicates that as one variable increases, the other tends to decrease.

While the strength of the relationship is a component of correlation, the statement in the correct choice encompasses the overall concept better than the others. The average of two datasets and the variation of a data set pertain to different statistical measures and do not reflect the notion of correlation. So, the correct choice accurately captures the essence of correlation in statistics.