Practice Test Geeks(CES) Certified Environmental Scientist Practice Test
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Environmental Sampling & Data Analysis Flashcards

7 cards from real CES practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Environmental Sampling & Data Analysis flashcards as text

  1. Which type of blank is used to identify contamination introduced during sample transport and field handling?

    Answer: Trip blank

    A trip blank accompanies samples during transport to detect VOC contamination introduced after collection, not during analysis.

  2. What is the purpose of calculating the Relative Percent Difference (RPD) in duplicate sample analysis?

    Answer: To measure precision between two replicate measurements

    RPD measures the variability (precision) between duplicate or replicate samples by expressing the difference as a percentage of the mean.

  3. In a soil gas survey, which sampling method is most appropriate for collecting volatile organic compound (VOC) vapor samples?

    Answer: Grab sampling with Summa canisters

    Summa canisters are electropolished stainless steel vessels used to collect instantaneous (grab) VOC vapor samples under evacuated conditions.

  4. Under EPA SW-846, what minimum purge volume is typically required before collecting a groundwater sample from a monitoring well?

    Answer: 3 well casing volumes

    Standard low-flow or traditional purging protocols require removing at least three well casing volumes to ensure the sample represents formation water.

  5. Which statistical test is appropriate to determine whether concentrations at a monitoring well are significantly higher than background concentrations?

    Answer: One-sided Welch's t-test

    A one-sided Welch's t-test (which does not assume equal variances) is used to test whether downgradient concentrations exceed upgradient background concentrations.

  6. A laboratory reports a result as '<2 µg/L' for a compound with a practical quantitation limit (PQL) of 2 µg/L. How should this non-detect be treated for statistical analysis?

    Answer: Apply a substitution method such as PQL/2 or maximum likelihood estimation

    Non-detects should be treated using established censored-data methods such as substituting half the detection limit or using maximum likelihood estimation (MLE), not simply excluded or zeroed.

  7. What does a surrogate spike recovery outside the acceptable window (e.g., 70–130%) indicate in an environmental sample?

    Answer: Matrix interference or extraction/analytical error may have affected results

    Poor surrogate recovery signals that matrix effects, extraction inefficiency, or instrument error may have compromised the accuracy of target analyte results.