One of the three options below is always checked when the "Elliptical stats" option is active:

*Use as Lines*: Assume all the plotted data represent line fits (i.e., are drawn from a bipolar distribution). Thus apply bipolar forms of the elliptical statistics to the data.*Use as Planes*: Assume all points represent plane or circle fits (i.e., drawn from a girdle distribution). Thus apply the girdle forms of the elliptical statistics (which produces the pole to the plane that best fits the data).*Combine Lines plus Planes*: Only available in the Least Squares Equal Area plot. As described below in the Statistics section, combine line and plane fits to get the best estimate of the desired magnetization component.

*Use as Lines*: All data shown will be assumed to represent line data (i.e., drawn from either a Fisher or a Fisher "Hemisphere" distribution)*Combine Lines and Planes*: (least squares only): Using the formulation of McFadden and McElhinny (1988) to combine line and plane or circle fits. This is discussed a bit more in the Statistics section. When this is selected, the "Use arc constraints" button is active; when checked, this restricts the points along plane or circle fits used to those along the arcs from about the last point used to about the antipode of the first point used (see the diagram in the description of the .lsq file format in the Formats section).

For example, the dialog above indicates that the test was performed on tilt-corrected directions, that these directions pass a common distribution test. (The calculated F of the F test exceeds F0.80; thus the null hypothesis would only be rejected at the 20% confidence level). The means differ by 12.7°ree;, much less than the 26.1°ree; critical angle, indicating that the data pass the reversal test at the 95% confidence limit. But the high value of the critical angle places this in the "indeterminate" classification of McFadden and McElhinny (1990a). The null hypothesis of a common mean would be rejected at or below the 53% confidence level.

Note that this code is not derived from the code that McFadden and McElhinny offer in their paper but was written from the algorithm described in the paper. Also, tests of the bootstrap code on data with identical concentration parameters yielded higher critical angles than those derived from the analytic equation for populations with a common concentration parameter. Thus the bootstrap test might pass data that should fail. The only test suggested by McFadden and McElhinny (1990a) not implemented here is the test for a single direction comprising one of the two groups.

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