Nigeria - National Survey of Agricultural Export Commodities 2003, First Round

The design employed a two-phase and a two-stage sample selection procedure

Phase 1, stage 1: The comprised listing exercise and administering of holding questionnaires. A total of 192 Local Government Areas (LGAs) were selected throughout the Federation and ten (10) Enumeration Areas (EAs) were selected in each LGA, totalling 1,920 EAs throughout the country including the Federal Capital Territory. Most of these LGAs were selected based on the information that they were producing one or more of the selected export crops. Not less than three LGAs were selected from each State of the Federation and FCT.

Phase 1, stage 2: In this stage, ten (10) export crop farming housing units were selected in each EA using systematic selection approach and all the households in each export crop farming housing unit were covered in the administration of holding questionnaires.

Phase 2, stage 1: This phase dealt with the crop cutting exercise which comprised farm survey, laying of yeild plot and harvesting. All the ten export crop farming EAs in the LGAs covered in the first phase were selected for crop cutting exercise.


No Deviation


On a national basis the 2003 survey achieved a response rate of about 74.86% at Housing Unit level.
Reasons for non-response was not given.


The formula adopted in calculating the design weights for the survey data (sample results) were as follows:

(i) The probability of selecting an EA within a state was obtained by dividing the total number of EAs sampled in a
state by total number of EAs in that particular state. Let this be represented by fj. That is,
fj = (Total Number of EAs sampled in a state)/(Total Number of EAs in that particular State)

(ii) Likewise, the probability of selecting an housing unit (HU) within an EA was obtained by dividing the total number
of housing units selected in an EA by the total number of housing units (HUs) listed in that particular EA. Let this be
represented by fk. That is,
fk = (Total Number of HUs selected in an EA)/(Total Number of HUs listed in that particular EA)

Then the product (fj) x (fk) represented by f is the sampling fraction for each of the corresponding study unit (Enumeration Area) for all the 1,920EAs canvassed throughout the 36 states of the Federation and FCT, Abuja. The inverse of the sampling fraction is known as the design weight and was applied accordingly to all the study units.

Mathematically,
Design weight = ((Total number of EAs in a state)/(Total number of EAs sampled in that particular state)) X ((Total Number of HUs listed in an EA)/(Total Number of HUs selected in that particular EA))

The above value was obtained for each of the 1,920 EAs canvassed throughout the 36 states of the Federation and FCT, Abuja.
The weight (Rf) was calculated and attached to the data

NOTE:
Adjustment was made to the weight depending on the reponse at household level