The method chosen for reference limit determination depends critically on which two factors?

• A. Sample size and distribution
• B. Temperature and humidity
• C. Instrument calibration and storage
• D. Publication year and lab

Answer: (A)

The method for setting reference limits hinges on the data you have: how many observations you collected and what their distribution looks like. With a large, roughly normal dataset, parametric methods are appropriate because you can rely on the mean and standard deviation to define the limits. If the sample is small or the data are skewed, nonparametric methods that estimate percentiles (like the 2.5th and 97.5th percentiles) or robust approaches that handle outliers are preferred. In short, the key factors are the sample size and the distribution shape, not external conditions. Factors such as temperature, instrument calibration or storage, or where the data came from can affect measurement accuracy, but they don’t dictate the statistical method used to determine reference limits.