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This chapter explores the fundamental concepts of sampling within the marketing research process. It discusses the importance of selecting a representative sample from a population to draw accurate inferences. Various sampling methods, including probability and non-probability sampling techniques, are outlined, highlighting when each should be used. Key terminologies, such as population, sample frame, and sampling unit, are clarified. By understanding these principles, researchers can enhance their data collection strategies and improve the reliability of their findings.
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Exploring MarketingResearch Chapter 16: Sampling - A Brief Introduction
Sampling • Sampling - the process of selecting a sufficient number of elements from the population so that, by studying the sample, we can infer the characteristics of the population. • Population characteristics are referred to astheparametersof the population and they are represented bysample statistics.
Why Sample? • Pragmatic Reasons • Budget and time constraints • Limited access to total population • Accurate and Reliable Results • Samples can yield reasonably accurate information • Strong similarities in population elements makes sampling possible • Sampling may be more accurate than a census • Destruction of Test Units • Sampling reduces the costs of research in finite populations.
Sampling Terminology • Population or universe - Any complete group: (people, sales territories, stores, etc.) • Population element - An individual member of a population • Sample - A subset of a larger population • Sample Frame - A list of elements from which the sample may be drawn • Sampling Unit - A single element or group of elements subject to selection in the sample
Learning Objectives • Know the steps in the sampling process. • Know the elements that make up a sampling plan.
Learning Objective • Understand the difference between probability and non-probability samples and why each would be used.
Probability versus Nonprobability Sampling • Probability Sampling • A sampling technique in which every member of the population has a known, nonzero probability of selection. • Sampling error is the amount of error that results due to the fact that no sample is a perfect representation of the population from which it is drawn. It is a function of sample size. • Only with a probability sample can we have confidence in the inferences we make about a population using sample data. • Nonprobability Sampling • A sampling technique in which units of the sample are selected on the basis of personal judgment or convenience; the probability of any particular member of the population being chosen is unknown.
Learning Objective • Be able to recognize an example of sampling frame error.
Learning Objective • Be able to recognize examples of the different types of probability and non-probability samples (i.e., simple random, stratified, systematic, quota, etc.), when each would be used and their advantages and disadvantages.
Probability Sampling • Simple Random Sampling • Assures each element in the population of an equal chance of being included in the sample. • Systematic Sampling • A starting point is selected by a random process and then every nth number on the list is selected. • Stratified Sampling • Simple random subsamples that are more or less equal on some characteristic are drawn from within each stratum of the population.
Proportional versus Disproportional Sampling • Proportional Stratified Sample • The number of sampling units drawn from each stratum is in proportion to the population size of that stratum. • Disproportional Stratified Sample • The sample size for each stratum is allocated according to analytical considerations.
Cluster Sampling • Cluster Sampling • An economically efficient sampling technique in which the primary sampling unit is not the individual element in the population but a large cluster of elements; clusters are selected randomly.
Nonprobability Sampling • Convenience Sampling • Obtaining those people or units that are most conveniently available • Judgment (Purposive) Sampling • An experienced individual selects the sample based on personal judgment about some appropriate characteristic of the sample member. • Quota Sampling • Ensures that various subgroups of a population will be represented on pertinent characteristics to the exact extent that the investigator desires.
Learning Objective • Understand the factors that should be considered when choosing a sampling method.
Degree of Accuracy Adaptation Appropriate Sample Design Resources Knowledge of Population Time What Is the Appropriate Sample Design?