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
A laboratory's method detection limit (MDL) study uses seven replicate analyses of a low-level spike. What statistical factor is applied to the standard deviation to calculate the MDL?
Answer: Student's t-value at 99% confidence for n-1 degrees of freedom
Per 40 CFR Part 136 Appendix B, the MDL equals the standard deviation of seven replicate spikes multiplied by the Student's t-value at the 99% confidence level with n-1 (6) degrees of freedom (t = 3.143).
Which sampling approach is most appropriate for characterizing the average concentration of a contaminant across a heterogeneous waste pile for disposal classification?
Answer: Composite sampling using multiple increments from across the pile
Composite sampling combines multiple increments from throughout the waste pile to produce a representative average concentration for waste classification purposes.
In environmental data analysis, what does the term 'censored data' refer to?
Answer: Measurements reported only as above or below a threshold value (non-detects or overrange)
Censored data are values known only to be above or below a reporting threshold, such as '1000 µg/L' (right-censored overranges).
Which type of quality control sample is used to verify that cross-contamination between samples does not occur during field equipment decontamination?
Answer: Equipment rinsate blank
An equipment rinsate blank (decontamination blank) is collected by passing reagent water through decontaminated field equipment to verify the decon procedure removed all prior contamination.
When a dataset fails the Shapiro-Wilk normality test, which non-parametric alternative to the one-sample t-test should be used to compare the median against a regulatory standard?
Answer: Wilcoxon signed-rank test
The Wilcoxon signed-rank test is the non-parametric equivalent of the one-sample t-test and is used when data are not normally distributed but are tested against a fixed value.
A matrix spike (MS) recovery of 140% for a soil sample analyzed for chlorinated solvents most likely indicates which condition?
Answer: The sample contains elevated native concentrations that interfere with the spike calculation
High MS recoveries (>130%) often result when native analyte concentrations in the sample are high relative to the spike, introducing error into the percent recovery calculation.
Which EPA method is the standard for measuring total suspended solids (TSS) in aqueous environmental samples?
Answer: EPA Method 160.2
EPA Method 160.2 is the standard gravimetric method for measuring total suspended solids (TSS) in water and wastewater by filtering and drying at 103–105°C.