Information from the survey is stored electronically in the form of data items. In some cases, items were formed directly from individual survey questions while in others, items were derived from answers to several questions (e.g. Body Mass Index derived from measured height and weight). Some items were derived with reference to information from other organisations such as the National Health and Medical Research Council (e.g. in relation to guidelines on consumption of alcohol).
Datasets from the National Health Survey are hierarchical in nature. A hierarchical data file is an efficient means of storing and retrieving information which describes one to many, or many to many, relationships e.g. a person may report multiple days on which alcohol was consumed and also multiple types of alcoholic beverages on each of these days.
Data about households and families are contained as individual characteristics on person records. While estimates are also available at the household level, estimates at the family level are not available from this survey. The data items and related output categories currently available for the NHS TableBuilder database, Basic CURF and Detailed Microdata (DataLab) are available in Excel spreadsheets from the Downloads tab of this product.
The following table shows the levels available in the microdata products and the information contained on those levels:
The following table shows the hierarchical file structure and the relationship between each level: