File Name: sampling and sample design .zip
- Methods of sampling from a population
- Sampling and non-sampling errors (and how to minimize them)
- Sampling Design
Methods of sampling from a population
In this paper, the basic elements related to the selection of participants for a health research are discussed. Sample representativeness, sample frame, types of sampling, as well as the impact that non-respondents may have on results of a study are described. The whole discussion is supported by practical examples to facilitate the reader's understanding. The essential topics related to the selection of participants for a health research are: 1 whether to work with samples or include the whole reference population in the study census ; 2 the sample basis; 3 the sampling process and 4 the potential effects nonrespondents might have on study results. We will refer to each of these aspects with theoretical and practical examples for better understanding in the sections that follow. In a previous paper, we discussed the necessary parameters on which to estimate the sample size. In turn, the target population corresponds to the entire set of subjects whose characteristics are of interest to the research team.
It would normally be impractical to study a whole population, for example when doing a questionnaire survey. Sampling is a method that allows researchers to infer information about a population based on results from a subset of the population, without having to investigate every individual. Reducing the number of individuals in a study reduces the cost and workload, and may make it easier to obtain high quality information, but this has to be balanced against having a large enough sample size with enough power to detect a true association. Calculation of sample size is addressed in section 1B statistics of the Part A syllabus. If a sample is to be used, by whatever method it is chosen, it is important that the individuals selected are representative of the whole population. This may involve specifically targeting hard to reach groups. For example, if the electoral roll for a town was used to identify participants, some people, such as the homeless, would not be registered and therefore excluded from the study by default.
Published on September 19, by Shona McCombes. Revised on February 25, Instead, you select a sample. The sample is the group of individuals who will actually participate in the research. To draw valid conclusions from your results, you have to carefully decide how you will select a sample that is representative of the group as a whole. There are two types of sampling methods:. You should clearly explain how you selected your sample in the methodology section of your paper or thesis.
Sampling and non-sampling errors (and how to minimize them)
By Saul McLeod , updated In psychological research we are interested in learning about large groups of people who all have something in common. We call the group that we are interested in studying our 'target population'. In some types of research the target population might be as broad as all humans, but in other types of research the target population might be a smaller group such as teenagers, pre-school children or people who misuse drugs. It is more or less impossible to study every single person in a target population so psychologists select a sample or sub-group of the population that is likely to be representative of the target population we are interested in. This is important because we want to generalize from the sample to target population. The more representative the sample, the more confident the researcher can be that the results can be generalized to the target population.
Clinical research usually involves patients with a certain disease or a condition. The generalizability of clinical research findings is based on multiple factors related to the internal and external validity of the research methods. The main methodological issue that influences the generalizability of clinical research findings is the sampling method. In this educational article, we are explaining the different sampling methods in clinical research. In clinical research, we define the population as a group of people who share a common character or a condition, usually the disease.
Published on September 19, by Shona McCombes.