Quality measures help users understand the quality of the 2011 Census results:
Response rates - the total number of usual residents whose details were completed on a returned questionnaire, divided by the estimate of the total number of usual residents. Prior to the census, ONS set a headline target of achieving 94 per cent response for England and Wales overall. Also includes coverage rates and return rates.
Item non-response - where respondents sometimes make errors when recording their answers, resulting in data that were not valid for estimation and analysis.
Item imputation - the process which corrected for any missing responses or inconsistencies.
Confidence intervals - indicators of the extent to which the estimate may differ from the true population value. The larger the confidence interval, the less precise is the estimate.
This section also includes how we assess the accuracy of answers with the Census Quality Survey, and information about data capture, coding and cleaning.