Читать книгу The Pocket Guide to Critical Appraisal - Iain K. Crombie - Страница 13

Surveys usually do not have a separate control or comparison group, so studies that have them are not surveys. However, in the analysis of surveys one subgroup in the sample may be compared against another (e.g. men versus women, or old versus young). Comparisons are being made, but there is no sense in which one group is acting as a control to another group. All the individuals have been selected at the same time and an internal comparison is made.