Nigeria - General Household Survey-Panel Wave 3 (Post Harvest) 2015-2016, Third round

The data cleaning process was done in a number of stages. The first step was to ensure proper quality control during the fieldwork. This was achieved in part by using the concurrent data entry system which was designed to highlight many of the errors that occurred during the fieldwork. Errors that are caught at the fieldwork stage are 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 sent from the state to the head office of NBS where a second stage of data cleaning was undertaken.
During the second stage the data were examined for out of range values and outliers. The data were also examined for missing information for required variables, sections, questionnaires and EAs. Any problems found were then reported back to the state where the correction was then made. This was an ongoing process until all data were delivered to the head office.
After all the data were received by the head office, there was an overall review of the data to identify outliers and other errors on the complete set of data. Where problems were identified, this was reported to the state. There the questionnaires were checked and where necessary the relevant households were revisited and a report sent back to the head office with the corrections.
The final stage of the cleaning process was to ensure that the household- and individual-level datasets were correctly merged across all sections of the household questionnaire. 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. The agriculture data were also checked to ensure that the plots identified in the main sections merged with the plot information identified in the other sections. This was also done for crop-by-plot information as well.
All completed and edited questionnaires by each team will remain in the custody of the field supervisor even after the data has been captured by data entry operators.
The supervisor will submit the completed and edited questionnaires to the NBS state officer. He /she will coordinate the forwarding of all completed questionnaires, softcopy records, laptops and printers to the NBS Headquarters in Abuja.

The CSPro software was used to design the specialised data entry program that was used for the data entry of the questionnaires.

The cleaning process at the head office was impeded by the fact that the questionnaires were not immediately available for inspection when problems were identified in the data . The
questionnaires were retained by the state in case there was the need for household revisits. So whenever problems were identified at the head office, the state office had to be contacted in order
to determine if the suspect data were the same as the information on the questionnaire, and to ensure that changes were captured in both places. This was a very cumbersome and time
consuming process since communication was difficult and in many instances the response was not timely.
Data cleaning and processing was an ongoing operation while the data were being collected in the field and after. Field staff and data entry operators were required to respond to data quality enquires from the Headquarters (HQ). There was a joint review of the data by HQ and field staff to ensure that the data collected is of the highest quality. The work of field staff (including data entry operators) were completed only when the data was signed-off as being satisfactory by the HQ and the World Bank.