Nigeria - National Core Welfare Indicators Survey, 2006, Third edition

Sample Design:
The National CWIQ Survey 2006 was designed with Local Government Area (LGA) serving as the reporting domain. Data were then aggregated to give estimates at Federal Constituency (FC), Senatorial, State, zonal (geo-political) and national levels.

Basically, a 2-stage cluster sample design was adopted in each LGA. Enumeration Areas (EAs) formed the 1st stage or Primary Sampling Units (PSUs) while Housing Units (HUs) formed the 2nd stage or Ultimate Sampling Units (USUs).

The EAs as demarcated by the National Population Commission (NPopC) for the 1991 Population Census served as the sampling frame for the selection of 1st stage sample units. In each LGA, a systematic selection of 10 EAs was made. Prior to the second stage selection, complete listing of Housing Units (and of Households within Housing Units) was carried out in each of the selected 1st stage units. These lists provided the frames for the second stage selection. Ten (10) HUs were then systematically selected per EA and all households in the selected HUs were interviewed.

The projected sample size was 100 HUs at the LGA level. The sample size using other defined reporting domains (FC, senatorial, state and geo-political zone) varied, depending on the number of the LGAs that made the reporting domain. Overall, 77,400 HUs were drawn at the national level. This made the survey the biggest in the history of the CWIQ.

SAMPLE SIZE FOR THE NATIONAL CORE WELFARE INDICATOR SURVEY

STATE LGAS EAS HUS
ABIA 17 170 1700
ADAMAWA 21 210 2100
AKWA IBOM 31 310 3100
ANAMBRA 21 210 2100
BAUCHI 20 200 2000
BAYELSA 8 80 800
BENUE 23 230 2300
BORNO 27 270 2700
CROSS RIVER 18 180 1800
DELTA 28 250 2500
EBONYI 13 130 1300
EDO 18 180 1800
EKITI 16 160 1600
ENUGU 17 170 1700
GOMBE 11 110 1100
IMO 27 270 2700
JIGAWA 27 270 2700
KADUNA 23 230 2300
KANO 44 440 4400
KATSINA 34 340 3400
KEBBI 21 210 2100
KOGI 21 210 2100
KWARA 16 160 1600
LAGOS 20 200 2000
NASARAWA 13 130 1300
NIGER 25 250 2500
OGUN 20 200 2000
ONDO 18 180 1800
OSUN 30 300 3000
OYO 33 330 3300
PLATEAU 17 170 1700
RIVERS 23 230 2300
SOKOTO 23 230 2300
TARABA 16 160 1600
YOBE 17 170 1700
ZAMAFARA 14 140 1400
FCT 6 60 600
TOTAL 774 7740 77400


The 7,740 EAs were selected directly from the population of EAs in the National Population Commission (NPopC) with equal probability of selection. Prior to selection, all the contiguous EAs were arranged serpentinely in each Local Government Area (LGA) of the state. This arrangement ensured that there was no overlapping between the LGAs and the EAs within the LGAs. With the frame so constructed, the EAs were cumulatively numbered to get the EA population. Therefore, 10 random starts (RS) were taken for each LGA and systematic selection approach were adopted in selection 10 EAs in each LGA.
A listing/updating exercise was carried out in each EA from where 10 housing units (HUs) were selected systematically to form the 2nd stage Sample or Ultimate interviewed using the Core Welfare Indicator questionnaire


Where is the local government estimate
N is the total number of EAs in the lth LGA in the state
n is the number of selected EAs in the lth LGA
H is the total number of Housing Units (HUs) listed from selected jth EA in lth LGA
h is the number of selected Housing Units (HUs) from jth EA in the lth LGA
is the value of the element of HU in the kth housing unit of jth EA in the 1th LGA.
is the weight

So the above will apply to all the individual members in order to give the population. However, the above weighting factor will be multiplied by average household size, when there is need to take the household aggregates to the population.
Estimate will be provided at LGA level.