Expand Your Knowledge: Using a Table to Test r The correlation coeffi cient r is a sample statistic. What does it tell us about the value of the population correlation coeffi cient r (Greek letter rho)? We will build the formal structure of hypothesis tests of r in Section 11.4. However, there is a quick way to determine if the sample evidence based on r is strong enough to conclude that there is some population correlation between the variables. In other words, we can use the value of r to determine if r ?