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Quantifying Uncertainty in Estimations of the Total Weight of Drugs in Groups of Complex Matrices: Using the Welch–Satterthwaite Equation
Author(s) -
Alberink Ivo,
Sprong Annette,
Bolck Annabel,
Vergeer Peter
Publication year - 2017
Publication title -
journal of forensic sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.715
H-Index - 96
eISSN - 1556-4029
pISSN - 0022-1198
DOI - 10.1111/1556-4029.13351
Subject(s) - standard deviation , relative standard deviation , statistics , absolute deviation , constant (computer programming) , work (physics) , mathematics , point (geometry) , computer science , standard error , thermodynamics , physics , geometry , detection limit , programming language
In this paper, a method is described to quantify estimations of the total amount of drugs in groups of seized items, including quantification of the precision. Previous work on this topic was based on the assumptions of normally distributed measurements and grouping of items with a common relative standard deviation. In practice, these assumptions are often violated, for example, for data with point masses at 0, or if certain items in a group have a very high standard deviation. The method described in this paper is based on work by Welch and Satterthwaite and does not assume constant relative standard deviations. Case examples are described for which the method is applied, and simulation studies are carried out for which both methods are applied. In the cases, both methods perform reasonably well. If the assumption of common relative standard deviations clearly does not apply, it is advised to use the method described.

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