Standard Deviations in Sampling and Analytical Methods
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Questions and Answers

What is the depth range of the soil samples collected in this study?

  • 0-5 cm
  • 10-20 cm
  • 0-10 cm (correct)
  • 5-15 cm
  • At each distance from the road, how many samples were taken and combined to form a single sample?

  • 5 samples
  • 20 samples
  • 10 samples (correct)
  • 15 samples
  • What is the purpose of combining the 10 samples taken at each distance into a single composite sample?

  • To increase sampling uncertainty
  • To decrease the total number of samples
  • To decrease sampling uncertainty (correct)
  • To increase the total number of samples
  • Why were samples collected at fixed distances from the road?

    <p>Both a and c</p> Signup and view all the answers

    What type of sampling plan is used in this study?

    <p>Systematic-judgmental sampling</p> Signup and view all the answers

    Which of the following is a type of sample that could have been collected in this study?

    <p>All of the above</p> Signup and view all the answers

    What is the main purpose of controlling pH, temperature, and light exposure when preserving samples?

    <p>To maintain the chemical composition of the samples</p> Signup and view all the answers

    Which of the following is NOT an example of a gaseous sample mentioned in the text?

    <p>Pharmaceutical products</p> Signup and view all the answers

    What is the main advantage of using stainless steel canisters or Tedlar/Teflon bags for urban air sampling?

    <p>Simplicity and representative sampling</p> Signup and view all the answers

    What is the primary reason that minimal preservation or preparation is needed for gaseous samples collected via solid sorbents, filters, or cryogenic cooling methods?

    <p>The samples are more stable due to the collection method</p> Signup and view all the answers

    How can the quantity of gaseous compounds collected via solid sorbents be determined?

    <p>By measuring the increase in sorbent mass if selective absorption occurs</p> Signup and view all the answers

    Which of the following is NOT an example of a solid sample mentioned in the text?

    <p>Compressed gases</p> Signup and view all the answers

    What is the primary advantage of stratified sampling over random sampling?

    <p>It reduces sampling error</p> Signup and view all the answers

    Which statement best describes systematic-judgmental sampling?

    <p>Sample sites are chosen systematically based on researcher judgment</p> Signup and view all the answers

    Which sampling method is most appropriate for preliminary or exploratory research?

    <p>Convenience sampling</p> Signup and view all the answers

    In stratified sampling, what is a stratum?

    <p>A subset of the population that shares a common characteristic</p> Signup and view all the answers

    Why might stratified sampling be used when one stratum has a low incidence relative to others?

    <p>To ensure that the low-incidence stratum is adequately represented</p> Signup and view all the answers

    In the study described, which sampling method was likely used to select sites for measuring pollutant concentrations in roadside soils?

    <p>Systematic-judgmental sampling</p> Signup and view all the answers

    What is the primary reason for the need for careful sampling when dealing with solids?

    <p>Solids are typically heterogeneous</p> Signup and view all the answers

    What is the purpose of the flexible metal leaves on the bottom of the gravity corer?

    <p>To prevent sediment from escaping as the corer is hauled back to the surface</p> Signup and view all the answers

    What is the purpose of the riffle shown in the example?

    <p>To divide a gross sample into four piles for further processing</p> Signup and view all the answers

    What is the purpose of the sample thief shown in the diagram?

    <p>To collect a sample of the sediment</p> Signup and view all the answers

    What is the primary reason for the importance of preservation mentioned in the text?

    <p>All of the above</p> Signup and view all the answers

    What is the primary purpose of the grab sampler shown in the diagram?

    <p>To collect a sample of the sediment</p> Signup and view all the answers

    What is the primary concern when designing a sampling plan for a quantitative analysis?

    <p>Accurately representing the composition of the target population</p> Signup and view all the answers

    Which of the following is NOT a consideration when designing a sampling plan?

    <p>The maximum amount of sample that can be collected</p> Signup and view all the answers

    What is a sampling error?

    <p>When the sample's composition is not identical to the target population</p> Signup and view all the answers

    In a homogeneous target population, what is true about the composition?

    <p>It is the same regardless of where, when, or the size of the sample</p> Signup and view all the answers

    In a qualitative analysis, what is the requirement for the sample?

    <p>There must be sufficient analyte present to ensure its detection</p> Signup and view all the answers

    When analyzing a trace-level component, what might be desirable when collecting samples?

    <p>Discriminating against major components</p> Signup and view all the answers

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