If a set of air samples has a wide confidence interval for the mean exposure, what does this indicate?

• A. High precision
• B. High certainty
• C. High variability or small sample size
• D. No variability

Answer: (C)

The width of the interval around the mean shows how precisely that mean has been estimated from the data. A wide interval means there is a lot of uncertainty about the true average exposure. This usually happens when the measurements are highly variable or when there aren’t many samples. In other words, high variability or a small sample size broadens the interval, reducing precision. It does not indicate high precision or high certainty; it reflects the opposite. If there were no variability, the interval would be narrow, not wide. To improve precision, you would increase the sample size or reduce measurement variability.