CIH CIH - Certified Industrial Hygienist Sampling Strategy and Statistical Analysis Questions and Answers 1 — Questions and Answers
Question 1: According to AIHA strategy guidelines, what is the primary purpose of a baseline survey in an industrial hygiene program?
- To immediately identify all overexposures
- To characterize exposures and assign workers to similar exposure groups (SEGs) (Correct answer)
- To satisfy OSHA recordkeeping requirements only
- To determine the need for administrative controls
Correct answer: To characterize exposures and assign workers to similar exposure groups (SEGs)
A baseline survey characterizes the range and central tendency of exposures and groups workers with similar exposure profiles into Similar Exposure Groups (SEGs) for further monitoring.
Question 2: What statistical distribution is most commonly assumed for occupational exposure data when performing lognormal analysis?
- Normal (Gaussian) distribution
- Lognormal distribution (Correct answer)
- Poisson distribution
- Binomial distribution
Correct answer: Lognormal distribution
Occupational exposure data typically follows a lognormal distribution because concentrations are always positive and right-skewed, meaning the logarithms of the values are normally distributed.
Question 3: What does the geometric standard deviation (GSD) indicate in occupational exposure data analysis?
- The average exposure concentration across all measurements
- The spread or variability of a lognormal exposure dataset (Correct answer)
- The ratio of the 95th percentile to the OEL
- The minimum number of samples required for statistical validity
Correct answer: The spread or variability of a lognormal exposure dataset
The GSD measures the variability (spread) of a lognormal exposure distribution; a GSD near 1.0 indicates little variability, while values above 3.0 suggest high day-to-day variability.
Question 4: In the AIHA exposure assessment strategy, what is the recommended minimum number of samples per SEG for a statistically defensible assessment?
- 3 samples
- 6 samples (Correct answer)
- 10 samples
- 25 samples
Correct answer: 6 samples
AIHA guidelines recommend a minimum of 6 samples per SEG to achieve statistically defensible estimates of the upper tail of the exposure distribution.
Question 5: What is the upper confidence limit (UCL) used to determine in occupational exposure assessment?
- The lowest expected exposure in a group
- Whether the true 95th percentile exposure likely exceeds the OEL (Correct answer)
- The arithmetic mean of all sample results
- The time-weighted average for the longest shift
Correct answer: Whether the true 95th percentile exposure likely exceeds the OEL
The UCL on the 95th percentile is used to determine with statistical confidence whether the true upper tail of the exposure distribution likely exceeds the occupational exposure limit.
Question 6: Which sampling approach should be used when a worker performs multiple tasks with different exposure levels throughout the day?
- A single full-shift sample only
- Task-based sampling with time-weighted averaging (Correct answer)
- Worst-case instantaneous grab sampling only
- Passive badge sampling at one location
Correct answer: Task-based sampling with time-weighted averaging
Task-based sampling measures exposures during distinct high- and low-exposure tasks separately, then calculates a time-weighted average across the full shift for OEL comparison.
CIH CIH - Certified Industrial Hygienist Sampling Strategy and Statistical Analysis Questions and Answers 1
According to AIHA strategy guidelines, what is the primary purpose of a baseline survey in an industrial hygiene program?