Designing A
Sampling Plan
A sampling
plan must support
the goals of an analysis. In characterization studies
a sample’s purity is often the most important parameter. For example,
a material sci- entist interested in the surface chemistry of a metal
is more likely
to select a freshly
exposed surface, created
by fracturing the sample under
vacuum, than a surface that has
been exposed to the atmosphere for an extended
time. In a qualitative analysis the sample’s composition does not need to be identical to that of the substance being analyzed, provided that enough sample
is taken to ensure that all components can be detected. In fact, when the goal of an analysis is to identify
components present at trace
levels, it may
be desirable to discriminate against
major components when sampling. In a quantitative analysis, however, the sample’s composition must accurately represent the
target population. The
focus of this
section, therefore, is on
designing a sampling plan for a quantitative analysis.
Five questions should be considered when designing a sampling
plan:
·
From where within the
target population should
samples be collected?
·
What type of samples
should be collected?
·
What is the minimum
amount of sample
needed for each
analysis?
·
How
many samples should
be analyzed?
·
How
can the overall
variance be minimized?
Each of these questions is considered below in more detail.
Related Topics
Privacy Policy, Terms and Conditions, DMCA Policy and Compliant
Copyright © 2018-2024 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.