Through ages, science has developed and advanced courtesy of theories, hypotheses, and conclusions of fact derived from replicating and generalizing individual research study findings. This is also true in nursing practice whereby research results said to have both internal and external validity have been applied to similar and dissimilar population groups. Many nursing studies employ a research design where a probability sample of a population is selected and studied and the evidence-based findings of the studies applied in the nursing practice. There has been increased clinical and epidemiological interest on the representativeness of study samples and the generalizability of research findings. This paper examines the sampling theory of research studies and discusses generalizability of such study results in the nursing industry.
Sampling theory is the study of the process involved in the selection of a representative subset of a population for purposes of studying the characteristics of the entire population (Gentles et al., 2015). Statistical research studies employ the concept of sampling theory in connection to hypothesis testing and generalizability whereby precise estimation of quantities is drawn from a probability sample of a population that represents the assessment of the whole population in question. Sampling approach is deemed feasible in conducting scientific studies as fair samples considered to present valid estimates of the population characteristics are studied. In this regard, the term population implies all cases or all persons from which a probability sample of all is drawn to obtain generalizable and representative sample estimates (Leung, 2015). Furthermore, logic dictates that “all” in this context must be numerically established from finite population boundaries. For example, a study to draw conclusions on the prevalence of asthma in secondary school-going children in a South-African state is an illustration of sampling. From a population of say 200 schools, during a given term date, 20 schools can be selected across the state and 10 students randomly chosen from each class. A questionnaire or interview is conducted and the data obtained is analyzed to give results. The results from the sample study group can be generalized as representative of the whole population of students from the 200 schools spread across the state.
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The internal and external validity of the research study is dependent on the boundaries chosen for a study population; hence it is important to care while establishing boundaries to eliminate bias or any other unintended adverse consequences. Validity implies the appropriateness of the study tools, processes, and data (Leung, 2015). Generalizability, therefore, can be assessed if the same criterion for validity has been adopted where the results in one study are applicable to another group under the proximal similarity and theoretical model (Leung, 2015). For instance, a study on the mortality of male British doctors aged above 35 years in relation to their smoking habits represents a specific study sample investigating the relationship between smoking and lung cancer deaths. The results of this study cannot be generalized to other population groups as the select study sample was of a non-representative nature and had specifically-defined boundaries. The results of the study must have been influenced by the description of the study population group and its characteristics hence raising questions on its generalizability. The argument for this proposition is based on the selection bias, information bias, and confounding consequences affecting the internal validity of the study. However, despite the fact that the British doctors are different in a number of ways from other population groups, the fundamental principle of the study is on the conclusion on the general impact tobacco smoke causes on human lungs and eventual mortality (Kukull & Ganguli, 2012).
The concept of sampling or representative sample can be taken to mean aspects such as miniature of a population, typical or ideal case averagely representing a population, general and unjustified approval for the data, and precise specification of a sampling scheme (Kukull & Ganguli, 2012). There are several concepts that are important in sampling theory that must be understood in the process of carrying out nursing research studies and these include target population, eligibility criteria, validity and reliability, sampling techniques, and representativeness of the sampled elements. The sampling technique highlights the strategies that are deployed in the process of acquiring a study sample and it is designed in such a way that biases are eliminated in order to increase representativeness.
In nursing research, it is important to understand concepts such as study population, research design, and setting because of they a critical in answering research questions and provide important information on the relevance of the research findings to the nursing practice (Kukull & Ganguli, 2012). Understanding these concepts provides nurses with the knowledge to examine the depth of research and equips the nurses with the competence to critically appraise the generalizability of research findings meant for consumption in the nursing practice.
References
Gentles, S. J., Charles, C., Ploeg, J., & Mckibbon, K. A. (2015). Sampling in qualitative research: Insights from an overview of the methods literature. The Qualitative Report , 20 (11), 1772-1789. Retrieved from http://www.miguelangelmartinez.net/IMG/pdf/2015_Gentles_Sampling_Qualitative_Research__TQR.pdf
Kukull, W. A., & Ganguli, M. (2012). Generalizability: The trees, the forest, and the low-hanging fruit. Neurology , 78 (23), 1886-1891. doi:10.1212/wnl.0b013e318258f812
Leung, L. (2015). Validity, reliability, and generalizability in qualitative research. Journal of Family Medicine and Primary Care , 4 (3), 324. doi:10.4103/2249-4863.161306
