In statistics, 'r' represents the correlation coefficient. The sample correlation coefficient, also known as r, R, or Pearson's r.'r' represents the linear relationship between two variables. It measures the direction and strength between two variables. It is also defined as co-variance of variables divide by the product of standard deviations.
Given the sample correlation coefficient value r is equal to 0.
It means there is no linear relationship between the body temperature and head circumference