NCJ Number: 
197321 


Title: 
Estimation of the Quantity of a Drug in a Consignment from Measurements on a Sample 


Journal: 
Journal of Forensic Sciences Volume:47 Issue:5 Dated:September 2002 Pages:968975 


Author(s): 
Colin G. G. Aitken Ph.D.; David Lucy Ph.D. 


Date Published: 
September 2002 


Page Count: 
8 


Publisher: 
http://www.astm.org 


Type: 
Report (Study/Research) 


Format: 
Article 


Language: 
English 


Country: 
United States of America 


Annotation: 
This paper describes procedures for selecting a sample size from
a drug shipment and, following examination of the contents of the
sample, for estimating the total quantity of drugs in the
shipment.



Abstract: 
The procedures described are used when a shipment of individual
packages is thought to contain illegal material, such as drugs,
in some or all of the packages. A sample from the shipment is
inspected, and the quantity of drugs in each package of the
sample is measured. The investigation must then estimate the
total quantity of drugs in the shipment. Since sampling variation
is present in the original measurements, it is not sufficient
just to adjust the sample mean pro rata. This paper describes an
analysis that takes into account the uncertainty regarding the
proportion of the packages that contain drugs and provides a
probabilistic summary of the quantity of drugs in the shipment.
The procedures described yield a probabilistic lower amount for
the quantity of drugs in the shipment, which is dependent on the
required standard of proof. The method described, which was
developed by Tzidony and Ravreboy (1992), considers the shipment
as a population and the constituent packages examined as a
sample. The quantities (weights) of drugs in the packages are
assumed to be random variables that are normally distributed,
with mean and variance. The mean quantity in a package in the
shipment is estimated by the mean of the quantities found in the
sample. A confidence interval is determined for the mean based on
the sample size, the sample mean, the sample standard deviation
of the quantities of drugs in the packages examined and an
associated tdistribution. An estimate of the total quantity of
drugs in the shipment is then determined by considering the size
of the shipment and the proportion of packages in the shipment
thought to contain drugs. A confidence interval may then be
constructed that may be said to contain the true quantity of
drugs with a given level of confidence. 2 figures and 14
references



Main Term(s): 
Technology transfer 


Index Term(s): 
Drug analysis; Drug law enforcement; Drug smuggling; Forensic sciences; Investigative techniques 







To cite this abstract, use the following link: http://www.ncjrs.gov/App/publications/abstract.aspx?ID=197321 

