A graphical test for the significance of differences between frequencies from different samples

For testing the significance of differences between frequencies from different samples, an ellipse can easily be constructed on the basis of a formula developed on the assumption that both observed samples are random samples from the same parent population and that the best estimate of the true proportion is the weighted mean proportion of the two samples. The ellipse provides a very rapid method for testing pairs of frequencies.The opinions expressed in this paper are those of the authors and are not to be construed as those of the Navy Department.