4.2 Sampling Frame

Before we start drawing samples, we must first define the concept of a sampling frame. This is a complete list of all individuals or units in the population of interest from which a sample is drawn. A sampling frame is the foundation for selecting a sample that is representative of the population under study. You can think of a sampling frame as the “pool” from which elements of the sample is drawn.

Example 7: Suppose a market researcher wants to study the shopping habits of students in Pretoria. The population he is interested in are all students at tertiary institutions in Pretoria. The sampling frame would be a complete list of all students currently registered at tertiary institutions in Pretoria.

Exercise: In each of the scenarios given below, describe the population and the sampling frame.

  1. An animal scientist wants to determine the average weight of male lions in the Kruger Park.
  2. A human resources professional wants to know the median salary earned by accountants in her company.
  3. A high school principal wants to identify the best learners in Grade 10 mathematics at his school in 2025.
  4. A forester wants to wants to estimate the volume of merchantable timber of the pine trees on his plantation.

A good sampling frame must exhibit the following characteristics:

  1. Completeness: The sampling frame should include every member of the population of interest.
  2. Accuracy: The information in the sampling frame should be up-to-date and correct.
  3. No duplicates: Each member of the population should appear exactly once in the sampling frame.
  4. Relevance: The sampling frame should align with the research question and population of interest.

Exercise: In each of the scenarios given below, evaluate the given sampling frame in terms of its completeness, accuracy, duplicates and relevance.

  1. A researcher wants to survey registered voters in a city about their voting preferences. They use a voter registration list from two years ago. However, many people have moved away, passed away, or changed their voter registration since then.
  2. A market researcher wants to study phone usage among adults in a city. They use a landline phone directory as their sampling frame. However, many people, especially young adults, rely exclusively on cellphones and are not listed in the directory.
  3. A company wants to survey its customers about satisfaction with their products. They use a customer database, but some customers appear multiple times due to different email addresses or accounts (e.g., one customer might have made purchases under both “” and “”).
  4. A researcher wants to study pet ownership habits in a city. They use a list of employees from an inner-city corporation as their sampling frame. However, this list only includes people who work at that company, who may not be representative of the broader population (e.g., they may live in flats or complexes that discourage owning pets).

Once a good sampling frame has been constructed, we can proceed with taking a sample. The next two sections will consider different sampling methods.

Important Notation: Note that we will be using \(N\) to denote the population size, and \(n\) to denote the sample size.