Standardize heart rate

"Standardization" is a data transformation that modifies values of (variable) \(x\) as:

$$\text{standardize}(x) = \frac{x-x_{mean}}{\sigma}$$

where \(x_{mean}\) is the mean value of the data, and \(\sigma\) is its standard deviation.

Standardization can be helpful when you don't know how to interpret an absolute value. For example, what does a heart rate of 78 beats per minute mean? Is it high, low, or average?

In this exercise, you'll calculate the mean and standard deviation of the heart rate data and create a new column of standardized heart rates to help answer this question.

The patient data is available in your environment as df_patients. The Statistics package has been imported for you with the using keyword.