A Commissioner's Guide to Probability Sampling for Surveys at USAID
Sampling is the process of studying a subset of a population for the purposes of describing or testing questions about a whole population. At USAID, sampling may be used to collect data for baselines, evaluations (both impact evaluations and performance evaluations), assessments that require survey data, and in some cases in indicator reporting. This document includes answers to common questions that the authors have been asked by USAID staff and is based on experience, best practice, and existing agency guidance. Some USAID bureaus have specific guidance for population-based surveys which is guidance targeted at practitioners. This guide reviews similar content at a simplified level to support commissioners of surveys.
The purpose of this document is to provide a foundational understanding of probability sampling to USAID staff to equip them as well-informed commissioners and consumers of surveys, evaluations, and other products (hereafter referred to as studies) that require probability sampling. We hope that it will serve as a resource for commissioners to make informed decisions about surveys and to use monitoring, evaluation, and learning (MEL) resources effectively.
The main audience for this document includes monitoring, evaluation, and learning specialists, Contracting Officer’s Representative (CORs), and Agreement Officer’s Representative (AORs). This document is intended to provide a general overview of sampling and related concepts of representative survey design. It is not official guidance. Rather, it represents good practices in the survey design field. It is not specific to any USAID initiative or requirement, nor is it exhaustive. When pursuing a representative survey for USAID or in collaboration with other organizations, remember that there are guidelines and requirements associated with the purpose of the survey, which depends heavily on the stakeholders involved.
The first step to a successful survey is to understand the data needs, existing requirements, and policies of all stakeholders. As the commissioner, if you are unsure about the information provided by the external survey team, or the team is unable to answer your questions directly or transparently, seek the assistance of a survey design expert. Survey design is a specialized skill set, even among monitoring and evaluation experts. As a commissioner of a survey, consider the composition of an evaluation or assessment team conducting a survey to ensure the team has the right mix of skills and equipped to identify potential issues in a survey you are overseeing.