The documentation for Tonga Population and Housing census 2021 mentions (in Administrative Document, section 2.4):
To improve data quality in data collection, TSD continue to use CAPI technology in data collection for the 2021 Population and Housing Census. This was the second time to use CAPI for Census followed the first time in 2016.
The Survey Solution software was identified as one of the best tools for data collection due to its capabilities of monitor data collection and data quality. Every completed questionnaire is sent to the respective supervisors to check and either rejects the questionnaire back to the interviewers if there are any errors/inconsistencies or approves the questionnaire if he/she is satisfied with the completed questionnaire. Rejected questionnaires are then verified and corrected by the interviewers with the respective household while they are still in the field, which ensures data quality is collected from the field by the interviewers.
The use of the GPS in the tablets, together with the capturing the photo of each visited house ensures the interviewers visited their correct Enumeration Area (EA) as well as proof of visiting the house. With the GPS points, Supervisors and Headquarters staffs were able to plot these GPS points on the map and identify those interviewers who may have enumerated in a wrong EA or had overlapped to other EAs assigned to another interviewer. In summary, improved data quality is attained through correcting survey processes during the field operation.
One of the biggest advantages of using Survey Solutions was the capability to allow for data collection to continue without internet access and this gives more flexibility for interviewers to undertake their work in areas without internet access and only synchronizes the completed questionnaires once they have access to the internet later. Ucall was the main service provider use for DATA by the tablet users.
The Questionnaire was designed using the Survey Solution Questionnaire Designer Tool, which has the facilities to include validations, consistency and logic checks as well as well-designed skip patterns to assist the interviewers in collecting good quality data.