2011 Census Data Quality Assurance Strategy: Plans and developments for the 2009 Rehearsal and 2011 Census

Paula Guy

BSPS 10th September 2009

Contents

• QA Strategy: objectives & prioritisation• QA Strategy: components • Comparator sources• Demographic analysis • Census Rehearsal• Next steps

Context: 2011 Quality Model

Designquality

Operational quality management

Quality assurance

Quality measurement

and reporting

Quality management

High quality

population statistics (as defined

by the CSFs)

Improvements since 2001

• Enhanced address register• Better management information• Wider enumeration base• More questions re: migration and second addresses

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

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

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

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

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:

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 QA Topic QA

Data flows: Questionnaire tracking, Address Register, Field reports, Administrative and Survey sources

Reconcile multiple responses within a HH

Scanning & recognition

Internet data capture

Implement contingency

LA Estimate

QA PanelReviewsLA, Regional and cumulative totals

Level 2 Topic & Demo QA

checks

QA Panel

Rejects

QA Panel

RejectsQA

Panel Accepts

Local Authority estimates QA process

Level 1 Topic & Demo QA

checks

Proceed to coverage imputation

Comparator data

0 10 20 30 40 50 60 70 80 90

Age coverage (0 to 90+ years)

Super older person databasePension credit claimants

Electoral register2001 CensusPrisoner data

Unemployment benefit claimsHome armed forces data

Foreign armed forces dataHigher education students data

School CensusChild benefit claimants

Pop'n est's by marital statusPatient register

Pop'n est's by ethnic groupRolled forward MYEs

Age coverage of Administrative Sources for 2011 Validation

Black = Within age group, all people are countedGrey = Within age group, looking at characteristicsWhite = Looking at sub-set of population

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

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

2001 Sex ratio validation: Southampton example

Source: ‘A Quality Assurance and Contingency Strategy for the One Number Census’, ONS

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

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

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