Mage et al. criticize our article (Barr et al. 2006), stressing six "... factual and conceptual errors that need to be called to the readers' attention." We appreciate their careful reading of our work, and they raise several important points regarding survey design. However, we take issue with some of their statements. Many investigations are designed to generalize the results of the research performed within a sample population to a larger population. In these types of investigations, enrollment of a representative sample is a necessary condition for making inferences to the larger population through known selection probabilities that are then used for applying sampling weights to study results. However, in order to generalize the results, these studies must have an adequate sample size, high response rate, and, importantly, a preliminary assessment of whether the factors for probability selection and weighting will be relevant to the condition being measured. Although representative samples are desirable and have been achieved in many studies, some studies in rare or difficult-to-reach populations cannot practically meet the criteria mentioned above.