Which option is NOT a valid use of confidence limits in exposure assessment?

Which option is NOT a valid use of confidence limits in exposure assessment?

• A. Determine the number of average exposures that exceed PELs
• B. Determine daily fluctuations in average exposure
• C. Determine cost effectiveness of controls
• D. Determine the range of the true mean with a given confidence

Answer: (C)

Confidence limits express how precisely an estimated average exposure reflects the true population mean. They give a range around the observed mean that, with a chosen level of confidence, contains the true mean. In exposure assessment this helps you judge risk and precision: if the upper bound of the interval is below the permissible exposure limit, you have evidence that the typical exposure is unlikely to exceed it; if the upper bound exceeds the limit, there is uncertainty about potential exceedances. They also inform understanding of day-to-day results by showing the expected variability around the mean and by indicating the range within which the true daily mean lies, based on the data. What they do not provide is guidance on economic decisions. Determining cost effectiveness of controls involves economic analysis—costs, savings, and cost-benefit calculations—not statistical estimates of exposure means. Confidence limits don’t address whether a control is worth implementing. So the use that does not fit is evaluating the cost effectiveness of controls.

Confidence limits express how precisely an estimated average exposure reflects the true population mean. They give a range around the observed mean that, with a chosen level of confidence, contains the true mean. In exposure assessment this helps you judge risk and precision: if the upper bound of the interval is below the permissible exposure limit, you have evidence that the typical exposure is unlikely to exceed it; if the upper bound exceeds the limit, there is uncertainty about potential exceedances. They also inform understanding of day-to-day results by showing the expected variability around the mean and by indicating the range within which the true daily mean lies, based on the data.

What they do not provide is guidance on economic decisions. Determining cost effectiveness of controls involves economic analysis—costs, savings, and cost-benefit calculations—not statistical estimates of exposure means. Confidence limits don’t address whether a control is worth implementing.

So the use that does not fit is evaluating the cost effectiveness of controls.