Pearson Correlation coefficient for simple correlation is a way of measuring the relationship between the two sets of information. The data are used form interval scale or ration scale. The symbol for Pearson's correlation is "ρ" when it is measured in the population and "r" when it is measured in a sample. Because we will be dealing almost exclusively with samples, we will use " " to represent Pearson's correlation unless otherwise noted. Pearson's r can range from -1 to 1.