One of the most important uses of statistical analysis is to investigate the associations or relationships between different variables. Understanding these relationships is of importance to an investigator for several reasons: It helps in the understanding of the phenomenon or phenomena under investigation. It gives insights into possible causal mechanisms between the variables. It is an important step in the construction statistical models which relate the variables to each other. These models may be used to improve the quality of predictions. The study of association in Statistics falls into two broad areas: 1. Correlation between two or more variables, and 2. Association between two or more categories in a frequency table.