In an ideal world, we could interview all beneficiaries. Since this would take too long and be too expensive, We can instead interview a sample of beneficiaries. If we do the sampling correctly, the data we get will represent the whole population of beneficiaries. To learn more about the principles of sampling, click here.
We have pre-prepared a sample design for you and created an Excel tool that will help you determine the sample size you need, which facilities/sites you should collect data from, and how many beneficiaries to interview at each of those facilities/sites. The sampling tool takes you through the steps you’ll need to design a sample for your survey. It will take you through the following decision-making process:
Decide whether to collect data at all facilities/sites or a selection of them: The sample size you will need will partly depend on whether you interview beneficiaries at all the facilities/sites or just some of them. If there are many facilities/sites in your program spread out across a large area, it may take too much cost and time to collect data from beneficiaries at all of them. In this case, you can collect data from a sample of the facilities/sites.
Determine the sample size: If you only interview beneficiaries at a random selection of facilities/sites, you will need to double your sample size.
- The minimum sample size when interviewing respondents from all facilities/sites is 100.
- The minimum sample size when interviewing respondents from a random selection of facilities/sites (selected using the sample selector tool) will be 200.
If you can interview more than the minimum sample, that will increase your precision. Use the sample size calculator provided to determine what sample size you should use.
Decide how many beneficiaries to interview at each facility/site and how to select them: The sample selector tool will tell you whether to interview every beneficiary, or select beneficiaries using an ‘interval.’ For example, you may need to select every fifth person.
Decide whether to collect data at the facility/site or at the beneficiaries’ homes
- Interviewing at the facility:
The most common way to implement a survey of beneficiaries is to interview the beneficiaries as they leave the facility, just after receiving the service. This means that data collection team members wait at the facility all day. The team will select beneficiaries according to the sampling guidance they have been trained in and ask selected beneficiaries permission to interview them just before they leave the facility.
- Interviewing at the beneficiaries’ homes:
If the facilities/sites serve very few beneficiaries per day, the data collection teams may have to wait at the facilities/sites for too long, making data collection expensive. An alternative is to have the facilities/sites collect the names and contact details of all the beneficiaries they serve over a one month period. You can then select the required number of respondents from the listed respondents at random. The data collection team will then visit these beneficiaries at their homes and interview them.
Whichever approach is used, the interviewers must find a private and comfortable place to conduct the interview, where the respondents know no one can hear their answers.