How to Investigate the Use of Medicines by Consumers
(2004; 98 pages) View the PDF document
Table of Contents
View the documentAcknowledgements
View the documentPreface
Open this folder and view contents1. Why study medicines use by consumers
Open this folder and view contents2. What influences medicines use by consumers
Open this folder and view contents3. How to study medicines use in communities
Open this folder and view contents4. Prioritizing and analysing community medicines use problems
Close this folder5. Sampling
View the document5.1 Introduction
View the document5.2 Selection of study sites and study units
View the document5.3 Purposeful sampling for qualitative studies
View the document5.4 Probability sampling methods for quantitative studies
View the document5.5 Bias in sampling
View the document5.6 Sample size
Open this folder and view contents6. Data analysis
Open this folder and view contents7. Monitoring and evaluating rational medicines use interventions in the community
View the documentBack cover

5.1 Introduction

Sampling involves the selection of a number of study units from a defined study population. When drawing a sample, a researcher first needs to decide which population (s)he intends to study. This depends on the research objectives and questions. Sampling strategies need to be defined as you can rarely cover every person in the selected population. In qualitative studies they aim to identify information-rich cases or informants. Information-rich cases are those from which one can learn a great deal about issues of central importance to the purpose of the research, so the term purposeful sampling is used when such people are selected.

For example, when understanding is needed of how infertile women cope, in-depth interviews should be conducted with women who experience infertility. Probability sampling typically depends on large samples selected randomly. A truly random and statistically representative sample allows for generalization from the sample to the larger population. The purpose of such sampling methods is not to gain in-depth understanding of an issue, but to be able to generalize findings. Such sampling can be stratified to ensure that all groups of interest are included.

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