Environmental Sampling Design - Fundamentals of Environmental Sampling and Analysis - page 64

2. Define ''representativeness'' and discuss how sample ''representativeness'' is dependent
on both the project objective and sample matrices? Give examples to illustrate.
3. Make a list of important factors (criteria) that are important in developing a sampling design
including where, when, and how many samples are collected?
4. Describe various reasons that can cause heterogeneity, that is, the difficulties in obtaining
representative samples from (a) surface water (river, stream, lake) and (b) atmosphere.
5. Describe various reasons that can cause heterogeneity, that is, the difficulties in
obtaining representative samples from (a) solids (e.g., soils) and (b) biological samples
(e.g., fishes).
6. Describe the differences between: (a) haphazard sampling; (b) judgmental sampling; and
(c) simple random sampling.
7. Define: (a) composite sampling; (b) transect sampling; and (c) search sampling.
8. Describe the advantages and disadvantages of (a) composite sampling and (b) systematic
sampling.
9. Describe the differences of three allocation methods used in stratified random
sampling: (a) equal allocation; (b) proportional allocation; and (c) optimal allocation.
10. Describe (a) the difference between systematic grid sampling and systematic random
sampling and (b) the method to calculate the mean and standard deviation from
systematic sampling.
11. Why the standard deviation is typically smaller for stratified random sampling than
simple random sampling, particularly for a heterogeneous population with a geographi-
cal (spatial) or temporal pattern?
12. In a site assessment for the identification of contaminated source, which one of the
following is likely the best and the least favorable: (a) judgmental sampling; (b) simple
random sampling; and (c) systematic random sampling? Briefly explain.
13. To confirm whether a site has been cleaned up or not, which one of the following is
likely the best and the least favorable: (a) judgmental sampling; (b) simple random
sampling; and (c) systematic random sampling? Briefly explain.
14. A petroleum refinery plant discharges toxic chemicals into a river at unknown periodic
intervals. (a) If water samples below the discharge pipe will be collected to estimate
the weekly average concentration of the effluent at that point, is simple random,
stratified random, or systematic sampling the best? Briefly discuss the advantages and
disadvantages of these three designs for this situation. (b) If the data objective is to
estimate the maximum concentration for each week of the year, is your choice of a
sampling plan different than in (a) where the objective was to estimate the weekly
mean? Briefly state why?
15. Given the following particular situation, identify which sampling design approach
should be used and discuss why this is the most appropriate?
(a) If you are performing a screening phase of an investigation of a relatively small-
scale problem, and you have budget and/or a limited schedule. Your goal is to assess
whether further investigation is warranted that should include a detailed follow-up
sampling.
(b) If you are estimating a population mean and you have known the existence of spatial
or temporal patterns of the contaminant. Your goal is to increase the precision of the