Large males of the European earwig, Forficula auricularia, develop abdominal forceps, which are used in fighting and courtship. Smaller males do not develop the forceps. Tomkins and Brown (2004) compared the proportion of males having forceps on islands in the North Sea with the population density of earwigs, measured as number caught per trap. Their data are listed in the following table.

a. The distribution of the two variables is not bivariate normal, and transforming the data does not improve matters. Choosing the most appropriate method, test whether the two variables are correlated.

b. What are your assumptions in part (a)?