Sampling in Research

Most statistics handbooks define a sample as a subset of elements drawn from a larger unit called a population. In this chapter, however, we use the term ‘sample’ in a broader sense. A sample is defined as the set of elements from which data is collected. We thus are interested in all types of samples; what­ever their size, their nature, the method of selection used and the aims of the study – from the sample comprising only one element, selected by judgement and intended for qualitative processing, to large-scale random sampling aimed at testing hypotheses using advanced statistical techniques. The chapter pre­sents the range of options open to the researcher when drawing a sample, and guides the researcher’s choice by indicating the main criteria to be taken into account.

Choices made when drawing a sample will have a determining impact on the external validity as much as the internal validity of the study. External validity refers to the possibility of extrapolating the results obtained from a sample to other elements, under different conditions of time and place. Internal validity consists in ensuring the relevance and internal coherence of the results in line with the researcher’s stated objectives. The validity of a study can be linked to three characteristics of the sample: the nature (heterogeneous or homogeneous) of the elements it is composed of; the method used to select these elements; and the number of elements selected.

Various methods can be used to establish a sample. These differ essentially in the way elements are selected and the size of the sample. Choices made con­cerning these two questions have implications in terms of both possible biases and the potential to generalize from the results. It therefore seems essential to be familiar with the various ways sample elements can be selected, and the criteria to consider when determining sample size, before deciding upon a sampling method.

Source: Thietart Raymond-Alain et al. (2001), Doing Management Research: A Comprehensive Guide, SAGE Publications Ltd; 1 edition.