Population Sampling 2008

Population Sampling 2008 - Population Sampling ESM 211...

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Population Sampling Population Sampling ESM 211
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Common failures in monitoring Common failures in monitoring programs (Elzinga et al. 2002) programs (Elzinga et al. 2002) Technical problems Poor design leads to inconclusive results Use of multiple or unreliable observers complicates interpretation of results Data are lost (including inability to interpret datasheets) Data are not analyzed Natural system fluctuation obscures change caused by management Institutional problems Premature termination of monitoring Inadequate resources to collect or analyze data Managers refuse to use monitoring data to make decisions Failure to place monitoring within a management framework leads to perception (or reality) that the data are irrelevant
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Population vs. Sample Population vs. Sample Sample True Population
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Confidence intervals Measure of precision 95% CI commonly used “95% chance that the true mean is in the CI”  (Bayesian) “If the sampling process is repeated many  times, the the CI will cover the true mean 95%  of the time” (Frequentist)
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Accuracy = Precision + Bias Imprecise  without bias Bias:  Does the mean of the estimates converge  to the true value? Precision: How variable are the estimates? Precise  with bias
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Pseudo-Replication A term often used in experimental studies, but also occurs when sampling natural populations, Replicate samples are the smallest units to which “treatments” are independently applied, When there is pseudo-replication, there is dependency among the replicated samples (beyond the treatments!),
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Hypothetical Population
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Clearly defined target population Biological population of
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Population Sampling 2008 - Population Sampling ESM 211...

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