1. 2011 Census Data Quality Assurance Strategy: Plans and developments for the 2009 Rehearsal and 2011 Census Paula Guy BSPS 10 th September 2009

2. Contents QA Strategy: objectives & prioritisation QA Strategy: components Comparator sources Demographic analysis Census Rehearsal Next steps

3. Context: 2011 Quality Model Design quality Operational quality management Quality assurance Quality measurement and reporting Quality management High quality population statistics (as defined by the CSFs)

4. Improvements since 2001 Enhanced address register Better management information Wider enumeration base More questions re: migration and second addresses

5. Data QA Strategy objectives: Ensure 2011 outputs are fit for purpose and meet user expectations Understand differences between Census population estimates and rolled-forward MYEs Ensure Census population characteristics are accurate Transparency Work in partnership with stakeholders Metadata including quality measures published with data

6. Planning and prioritisation of data QA to meet these objectives: Monitor information and data from field operations Identify and monitor data at key processing stages Prioritise QA of data items critical for Census population estimates, including coverage adjustment Prioritise LADs where data uncertainty is concentrated, including uncertainty around MYEs, and process them early Flexible deployment of QA resource Automation of QA checks as far as possible

7. Topic QA To quality assure detailed level Census data to address errors such as respondent or enumerator error or those introduced by processes such as data capture, edit or imputation. Includes item-level data, low level geographies and multivariate analysis of specified population subgroups. Demographic QA To quality assure national, regional and Local Authority District census estimates, drawing on external sources, using demographic indicators and guided by the input and direction of an expert QA panel

8. Overlaps between Topic & Demographic QA Young men International migrants (short and long term) Students Residents and staff in Communal Establishments Minority ethnic groups Private renters People with a second address Babies under 1 Over 85s Armed forces Priority subgroups

9. Overlaps between Topic & Demographic QA cont … Lots of holiday homes Caravan sites Second residences High multi-occupancy Regeneration areas Low enumeration or high variability of response High population change ‘Priority LAs’ identified by areas with:

10. Demographic and Topic QA Data load Apply derivations & filters Item imputation Coverage estimation Coverage imputation Post-adjustment imputation Apply complex Derived Vars Assign output geographies Disclosure control adjustment Demographic QATopic QA Data flows: Questionnaire tracking, Address Register, Field reports, Administrative and Survey sources Reconcile multiple responses within a HH Scanning & recognition Internet data capture

11. Implement contingency LA Estimate QA Panel Reviews LA, Regional and cumulative totals Level 2 Topic & Demo QA checks QA Panel Rejects QA Panel Accepts Local Authority estimates QA process Level 1 Topic & Demo QA checks Proceed to coverage imputation

12. Comparator data Black = Within age group, all people are counted Grey = Within age group, looking at characteristics White = Looking at sub-set of population

13. Additional sources for QA –International Passenger Survey –ONS survey data sources –University halls of residence capacity data –CLG Gypsy/ traveller numbers –Address Register –Council tax data –CORE HA and LAD properties and tenants data

14. Demographic analysis at national & sub- national level Age/sex specific fertility rates and summary measures Age/sex specific mortality rates and summary measures Age specific sex ratios Age/sex in-migration rates Cohort change over time across censuses

15. 2001 Sex ratio validation: Southampton example Source: ‘A Quality Assurance and Contingency Strategy for the One Number Census’, ONS

16. Census Rehearsal Basic demographic analyses Ethnicity and marital status by age & sex Frequency of households and CEs, including HH by tenure CE residents by age Home Armed Forces by age and sex Prisoners by age and sex Students by age and sex Migration – LT, ST, Internal, International and Cross- border by age and sex Caravans/caravan residents Traveller counts

17. Next steps Rehearsal Plan for LA engagement Contingency strategy and admin data linkage Determine QA checks for 2011 Topic expert input Assess and secure comparator data sources Methodological input on tolerances and diagnostic ranges

18. Thank you The 2011 Census Data Quality Assurance Strategy is now available at: http:// www.ons.gov.uk / census / 2011-census / process-info / data-quality-assurance / index.html