Does R Change In Stats If Units Change

R Programming

When it comes to statistics, one of the fundamental concepts is the correlation coefficient, also known as “r.” This coefficient measures the strength and direction of the relationship between two variables. However, the question often arises: Does the value of r change if the units of measurement for the variables change?

Firstly, it’s important to understand that the correlation coefficient, r, is unitless. This means that it does not depend on the units in which the variables are measured. Whether we measure variables in inches, meters, dollars, or any other unit of measurement, the value of r will remain the same.

Let’s dive deeper into why this is the case. The formula for calculating r involves standardizing the variables by converting them to z-scores. These z-scores are calculated using the mean and standard deviation of each variable, effectively removing the original units of measurement. As a result, the final value of r is a pure number, unaffected by the specific units in which the original variables were measured.

For example, let’s consider a scenario where we have two variables: height and weight. If we initially measure height in centimeters and weight in kilograms, and then decide to re-measure height in inches and weight in pounds, the correlation coefficient between height and weight will not change.

It’s fascinating to realize that this property of the correlation coefficient holds true regardless of the units used for measurement. Whether we’re dealing with physical measurements, financial data, or any other type of quantitative information, the value of r remains constant.

In my experience, understanding this concept has been crucial in my statistical analyses. Knowing that the correlation coefficient is independent of units has provided clarity and confidence in interpreting the strength and direction of relationships between variables.


In conclusion, the value of the correlation coefficient, r, does not change when the units of measurement for the variables change. This intrinsic property of r being unitless allows for consistent interpretation of the strength and direction of relationships between variables, regardless of the specific units employed. Embracing this aspect of statistical analysis enhances the robustness and reliability of our insights.