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Overview of the Census of Population
Chapter 7 – Processing
Table of contents
The step after collection, known as the processing phase, began May 3 with the process of transforming responses from approximately 13.5 million households into meaningful data.
Receipt and registration
For the 2011 Census, electronic questionnaires were transmitted directly to servers at Statistics Canada's Data Operations Centre (DOC) and registered automatically upon receipt. Paper questionnaires that were returned by mail were registered by Canada Post by scanning the bar code on the front of the questionnaire before delivery to the DOC. To confirm receipt by Statistics Canada, the questionnaires were removed from the envelopes and scanned again at the DOC.
Registrations were transmitted to the Master Control System (MCS) daily. The MCS then notified enumerators (via the Field Management System) which questionnaires had been received so they did not contact these respondents during non-response follow-up (NRFU) procedures.
Questionnaires that were completed by enumerators during NRFU were shipped from the local census offices (LCOs) across the country to the DOC where they were scanned and registered.
Often, the DOC received multiple responses (i.e., multiple questionnaires) for one household. These could have been valid responses (e.g., a supplementary questionnaire that contains information about additional household members) or invalid responses (e.g., a duplicate questionnaire for the household was completed by another household member). These situations were flagged and handled in the 'Edits' processing step described in the Edits section which follows in this chapter.
Imaging and data capture
Once paper questionnaires were registered, they were loaded onto carts and moved to the next step for document preparation and scanning.
- Document preparation – Mailed-back questionnaires were removed from envelopes. In order to ensure that questionnaires were ready to be scanned, operators removed foreign objects such as clips and staples from the documents. Forms were also separated in half (Census of Population) or into single sheets (Census of Agriculture) using guillotines (large paper cutters).
- Scanning – Scanning, using high speed scanners, created digital images from the paper questionnaire.
- Automated image quality assurance – An automated system verified the quality of the scanning for capture purposes. Images failing this process were flagged for rescanning.
- Automated data capture – Optical Mark Recognition (OMR) and Intelligent Character Recognition (ICR) were used to extract respondent data. When the system could not recognize the handwriting (known as the write‑ins), data repair was done by an operator. Paper forms that could not be scanned (e.g., too damaged) or were filled out with a pen or pencil that could not be read by the automated capture systems, were sent for transcription.
- Check‑out – This quality assurance process ensured that the questionnaire images and captured data were of sufficient quality and that the paper questionnaires were no longer required.
As the data were captured, an interactive process of manual and automated edits was performed to ensure that problems and inconsistencies were identified and resolved.
- Blank and minimum content – This automated edit identified questionnaires with no information or insufficient information to continue processing. These cases were returned to the field for non-response follow-up (NRFU) by census enumerators.
- Multiple responses – This automated edit identified households with one or more missing questionnaires. These cases were held in a queue until all questionnaires were received.
- Coverage edits – These edits ensured that the number of household members reported was consistent with the responses provided, including the number of names listed in the household roster. Errors were resolved by an automated process or through interactive verification by DOC staff by manually examining the captured data and scanned images (where available) to help determine the appropriate solution.
- Failed edit follow-up (FEFU) – Household questionnaires that needed further coverage or content clarification were transmitted to a collection support office for FEFU collection using a Computer‑assisted Telephone Interview (CATI) application. The data were transmitted back to the DOC and reintegrated into the system for subsequent processing.
Written responses were converted to numerical codes before they could be tabulated for release purposes. For the 2011 Census, all written responses on the questionnaires underwent automated and computer-assisted coding to assign each one a numerical code using Statistics Canada reference files, code sets and standard classifications. Reference files were built using actual responses from past censuses for the automated match process. Subject-matter experts supervised the interactive coding of responses that were not matched automatically with the reference files.
Edit and imputation
The data collected in any survey or census contains omissions or inconsistencies. These errors can be the result of respondents missing a question, or they can be due to errors generated during processing.
After the initial editing and coding operations were completed, the data were processed through the final edit and imputation activity. The final editing process detected errors and the imputation process corrected them.