Each data file contains two weights

• Ungrossed weight, which weights to the achieved sample size
• Grossed weight, which weights to the UK population.

These take into account (i) survey non-response, correcting for biases in the results caused by particular groups in the sample not responding to the survey, (ii) UK population characteristics, correcting for differences between the characteristics of the sample and the UK population, and (iii) day of week and month, correcting for variations in the sample size by day of week and month.

Additionally the household data file has three versions of these weights, the first for those households where respondents kept diaries, the second for those households where respondents kept worksheets, and the third for those households where respondents kept both diaries and worksheets.

This page last revised: Thursday 2 September 2003