Environmental Engineering Reference
In-Depth Information
Chapter 1
Study Design and Logistics
David A. Haukos
Abstract Reliable knowledge is critical for management and conservation of
wetlands. Essential to the scientific method and achieving reliable knowledge is
study design. The primary purpose of study design is the collection of data in an
unbiased and precise manner for an accurate representation of a population. Proper
study design includes formulation of study questions and objectives, hypotheses to
explain an observed pattern or process, conceptual models, appropriate methodology,
and a data management plan. Inference of study results and conclusions can be
explicitly bounded by defining an appropriate target population. Deductive, Induc-
tive, and Retroductive reasoning are used to infer study results to target populations.
Development of multiple competing hypotheses capable of being tested is at the core
of the hypothetico-deductive approach that maximizes potential knowledge from a
study. Selection of independent and dependent variables to test hypotheses should be
done with cost, efficiency, and understanding of the wetland system being studied.
Study type (e.g., experimental, observational, and assessment) influences the cer-
tainty of results. Randomization and replication are the foundation of any study type.
In wetlands, impact studies (e.g., BACI [before-after/control-impact] design) are
common and usually follow unforeseen events (e.g., hurricanes, wild fire, floods).
Sampling design is dictated by study objectives, target population, and defined study
area. A robust sampling effort is essential for accurate data. Reduction in statistical
and mechanical errors and data management protocols are overlooked features of
study design. In addition to statistical tests, estimation of the magnitude (i.e., effect
size) of an effect is crucial to interpretation of study results. When judging the merits
of results from a study, investigators should independently assess the hypothesis,
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