Correlation Correlation Examining the relationships between variables forms an important part of much biological research. For example, a c test is used to look for an association between categorical variables. However, we are often interested in the relationships between interval variables. All of these examples represent the simplest cases, i.e. relationships between pairs of variables.
More complex relationships involving more than two variables are possible.
If we wish to investigate these types of relationship we must make use of multivariate statistical methods. Consider the following scatter graph which gives a pictorial representation of the relationship between two variables x and y . There are many questions which could be asked. We can attempt to answer these questions using the techniques of regression and correlation analysis. Computationally the two methods are very similar but there are some important differences in the underlying assumptions about the nature of the relationship between x and y .