A string of dots, with each dot representing a single observation, can be used instead of bars. Add the Great Circle direction to the Rose Diagram. Proceed with analysis only if the Rayleigh test indicates that there is a significant mean direction to the data. Examine the Rose Diagram. Data analysis to this point has been an exercise in descriptive statistics.
More complicated procedures are necessary to continue.
If the data are not obviously skewed or bimodal, proceed to Decision Rules. Methods for Western Population Assuming that the goal of the butterflies is the overwintering sites in Mexico, start at step 1 for eastern population. Proceed to step 2 for eastern population. Local preferred directions of migrating Monarch butterflies may be Great Circle routes to their goal. He found that at a number of sites the mean direction of the migrants could not be distinguished from the Great Circle direction to the overwintering sites.