After geological or soil evidence has been recovered and analyzed, the next step is to synthesize the data, make any necessary comparisons, and interpret the likely significance of the results. The alternative possibilities that they originate from the same immediate source, from the same ultimate geological source but different immediate sources, or from different geological sources that contain indistinguishable material, often cannot be discriminated on the basis of examination of the trace evidence alone. Multivariate analysis methods can be used when several measurements are made on each individual or object, such as a soil sample, and are usually employed when considerably more than two samples are to be compared. The measurements may relate to different aspects of the same attribute, or to distinctly different attributes measured on different scales and considered in combination.