UK DATA ARCHIVE: IMPORTANT STUDY INFORMATION

Study Number 5140 - National Diet and Nutrition Survey : Adults Aged 19 to 64 Years, 2000-2001


DATA PROCESSING NOTES


Data Archive Processing Standards

The data were processed to the UK Data Archive's A standard. A rigorous and comprehensive series of checks was carried out to ensure the quality of the data and documentation.Firstly, checks were made that the number of cases and variables matched the depositor's records. Secondly, checks were made that all variables had variable labels and all nominal (categorical) variables had value labels. Where possible, either with reference to the documentation and/or in communication with the depositor, absent labels were created. Thirdly, logical checks were performed to ensure that nominal (categorical) variables had values within the range defined (either by value labels or in the depositor's documentation). Lastly, any data or documentation that breached confidentiality rules were altered or suppressed to preserve anonymity.

All notable and/or outstanding problems discovered are detailed under the 'Data and documentation problems' heading below.

Data and documentation problems

Missing values:
For many variables throughout the dataset, missing value codes are unlabelled. Unless otherwise stated, these may signify:
-9 non-response to whole event (e.g. blood not taken)
-8 not applicable (e.g. date of event = NA)
-6 record type does not exist

These variables may or may not be defined as 'missing' within the data, so users should treat them with caution. See also documentation for further details.

Useful Notes

This dataset contains a 'Nutrient Databank' as part of the documentation. The Food Standards Agency have supplied the following information for file onswave4.xls:
This file is for information/reference only. It contains the nutrient composition data which was used in conjunction with consumption data to report nutrient intakes in the survey. The structure of the file is as follows:
code number\subsidiary food group to which the code belongs\food name\base value\edible portion\units\dilution factor\maximum weight\

Data conversion information

From January 2003 onwards, almost all data conversions have been performed using software developed by the UKDA. This enables standardisation of the conversion methods and ensures optimal data quality. In addition to its own data processing/conversion code, this software uses the SPSS and Stat/Transfer command processors to perform certain format translations. Although data conversion is automated, all data files are also subject to visual inspection by a UKDA data processing officer.

With some format conversions data, and more especially internal metadata (i.e. variable labels, value labels, missing value definitions, data type information), will inevitably be lost or truncated owing to the differential limits of the proprietary formats.A UKDA Data Dictionary file (in rich text format), corresponding to each data file, is usually provided for viewing and searching the internal metadata as it existed in the originating format. These files are called: [data file name]_UKDA_Data_Dictionary.rtf

Important information about the data format supplied

The links below provide important information about the format in which you have been supplied the data. Some of this information is specific to the ingest format of the data, that is the format in which the UKDA was supplied the data in. The ingest format for this study was SPSS

Please click below to find out information about the format that you have been supplied the data in.

SPSS (*.por)

STATA (*.dta)
Tab-delimited text (*.tab)
MS Excel (*.xls files)
SAS (supplied as *.dat and *.sas)
MS Access (*.mdb files)

Conversion of documentation formats

Electronic and paper documentation supplied with this study is usually incorporated into the UKDA User Guide (in PDF format). The conversion programmes used are the latest versions of Adobe PDF Writer for electronic documentation and Adobe Paper Capture (Acrobat 'plugin' version) for paper documentation. Occasionally, someof the electronic documentation cannot be usefully converted to PDF (e.g. MS Excel files with wide worksheets) and this is supplied ina more appropriate format. All User Guides are fully bookmarked.