Round 1 Sample Design
In Nigeria, the PMA2020 survey collects data at the state-level to allow for the estimation of key indicators to monitor progress in family planning at the population and the service delivery points (SDPs) levels. The resident enumerator (RE), PMA’s female data collector, model enables replication of the surveys on an annual basis, or more frequently.
For PMA2016/Nigeria (National) R1, the project used a two-stage cluster design and drew a sample of enumeration areas (EAs) from the National Population Commission (NPopC) master sampling frame to achieve a representative sample of each state. This was the first round in Anambra, Kano, Nasarawa, Rivers, and Taraba states and the third round in Lagos and Kaduna states where the same EAs were used from previous rounds. The EAs were selected systematically using probability proportional to size. The NPopC provided the selection probabilities for the PMA2020 sampled clusters which were used to construct sample weights.
In each selected EA, households and private health facilities were listed and mapped. Field supervisors randomly selected 35 households (40 in Lagos) from the household listing using a random start method. A household roster was completed and all eligible women age 15-49 in selected households were approached and asked to provide informed consent to participate in the study.
For the service delivery point (SDP) survey, up to three private SDPs, including pharmacies, within each sampled EA cluster boundary were randomly selected from the listing. In addition, three public health SDPs (lowest, second-lowest and third-lowest level) designated to serve each EA population were selected.
Round 2 Sample Update
For this round of PMA2020 data collection - which was the second round in Anambra, Kano, Nasarawa, Rivers, and Taraba states and the fourth round in Lagos and Kaduna states - the same sample of enumeration areas (EAs) from previous rounds was used. A new random selection of 35 households (40 in Lagos) was drawn from the listing. A household roster was completed and all eligible women age 15-49 in selected households were approached and asked to provide informed consent to participate in the study.
The majority of SDPs are repeated in each round, forming a panel survey. If an EA had more than three private SDPs identified during the listing process, then a new sample of the private SDPs is selected during each round.
PMA2020/Nigeria continued in the two selected states: Kaduna and Lagos. No adjustments were made to the household sample size in Kaduna. After Round 1 in Lagos, however, a shortfall in the targeted sample size was observed, with only 771 completed female interviews. This was subsequently determined to be the result of a lower-than-expected response rate (75% among households and 89% among women). In addition, while one woman per household was assumed, it was much lower in Lagos. For Round 2, therefore, a few adjustments were made to calculate the required sample size: a new DEFF estimate of 2.03 was applied; the average number of eligible women per household was assumed to be 0.90; and the take size was raised to 40 households per EA cluster. The resulting required sample size was 1791 women from 50 EA clusters. Considering low response rates during Round 1, a total of 52 EA clusters – 37 from Round 1 and additionally selected 15 – were included for implementation in Round 2 and onward. The final completed sample included 10,063 households (97.2% response rate) and 11,380 de facto females (98.7% response rate). Data collection was conducted between April and May 2017. The majority of SDPs are repeated in subsequent rounds, forming a panel survey. If an EA had more than three private SDPs identified during the listing process, then a new, random sample of three private SDPs is selected during each round.