Nigeria - Nigeria Living Standards Survey 2018-2019

CAPI: The 2018/19 NLSS was conducted using the Survey Solutions Computer Assisted Person Interview (CAPI) platform. The Survey Solutions software was developed and maintained by the Development Economics Data Group (DECDG) at the World Bank. Each interviewer and supervisor was given a tablet which they used to conduct the interviews. Overall, implementation of the survey using Survey Solutions CAPI was highly successful, as it allowed for timely availability of the data from completed interviews and real-time quality checks.

DATA COMMUNICATION SYSTEM: The data communication system used in 2018/19 NLSS was highly automated. Each field team was given a mobile modem to allow for internet connectivity and daily synchronization of their assignments and completed interviews. This ensured that headquarters in Abuja had access to the data in real-time. Once each interview was completed and uploaded to the server, the data was first reviewed by the data editors. The data was also downloaded from the server, and Stata dofiles run on the downloaded data to check for additional errors that were not captured by the Survey Solutions application during data collection and entry. An excel error file is generated following the running of the Stata dofiles on the raw dataset. Information contained in the excel error files are communicated back to respective field interviewers for action by the interviewers. This action was done on a daily basis for the duration of the survey.

DATA CLEANING: The data cleaning process was done in three main stages. The first stage was to ensure proper quality control during the fieldwork. This was achieved in part by incorporating validation and consistency checks into the Survey Solutions application used for the data collection and designed to highlight many of the errors that occurred during the fieldwork.

The second stage cleaning involved the use of data editors and data assistants. As indicated above, once the interview is completed and uploaded to the server, the data editors review completed interview for inconsistencies and extreme values. Depending on the outcome, they can either approve or reject the case. If rejected, the case goes back to the respective interviewer’s tablet upon synchronization. Special care was taken to see that the households included in the data matched with the selected sample and where there were differences, these were properly assessed and documented. Additional errors observed were compiled into error reports that were regularly sent to the teams. These errors were then corrected based on re-visits to the household on the instruction of the supervisor. The data that had gone through this first stage of cleaning was then approved by the Data Editor. After the data editor’s approval of the interview on Survey Solutions server, the Headquarters also reviews and depending on the outcome, can either reject or approve.

The third stage of cleaning involved a comprehensive review of the final raw data following the first and second stage cleaning. Every variable was examined individually for (1) consistency with other sections and variables, (2) out of range responses, and (3) outliers. However, special care was taken to avoid making strong assumptions when resolving potential errors. Some minor errors remain in the data where the diagnosis and/or solution were unclear to the data cleaning team.