The Interpretation Of Refractive Index Measurements. Iii.

The question of whether or not to group recovered glass fragments before comparison with a control sample is fundamental to the interpretation of refractive index measurements. A computer program has been written to perform the grouping and explore the consequences. Grouping the fragments is shown to increase the chances of finding all recovered fragments similar when they have in fact come from the same source as the control, and to give enhanced discrimination when the recovered glass has come from a different source. When the recovered fragments have come from two different sources the consequences of the grouping procedure are preferable to non-grouping.