How can science be done by surveys and is cluster sampling nonsense?
Surveys are at the heart of epidemiological studies in which prevalence information (how often a disease or trait – or death– occurs) is not available through centralized sources. One of the most widely cited surveys in the US is the National Health and Nutrition Examination Survey which estimates a variety of information, from how many Americans have Diabetes to who uses pesticides. This is carried out under the auspices of the National Center for Health, which is in turn under the CDC. While, in theory, some of this information is available through other sources – doctors, for example, could report how many of their patients are treated for diabetes – there is no way of centrally recording the information and making sure that everyone with diabetes is actually counted. As a consequence, statistics have been developed to solve this problem. Cluster sampling is a well-established in statistics, and is routinely used to estimate casualties in natural disasters or war zones. For the Iraq
