Sampling And Sample Design Pdf

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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.

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.

Sampling and Sample Design

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. One of the problems that can occur when selecting a sample from a target population is sampling bias. Sampling bias refers to situations where the sample does not reflect the characteristics of the target population. Many psychology studies have a biased sample because they have used an opportunity sample that comprises university students as their participants e.

But who are you going to try it out on and how will you select your participants? There are various sampling methods. The one chosen will depend on a number of factors such as time, money etc. Random sampling is a type of probability sampling where everyone in the entire target population has an equal chance of being selected.

This is similar to the national lottery. Random samples require a way of naming or numbering the target population and then using some type of raffle method to choose those to make up the sample. Random samples are the best method of selecting your sample from the population of interest. The researcher identifies the different types of people that make up the target population and works out the proportions needed for the sample to be representative.

A list is made of each variable e. IQ, gender etc. For example, if we are interested in the money spent on books by undergraduates, then the main subject studied may be an important variable. For example, students studying English Literature may spend more money on books than engineering students so if we use a very large percentage of English students or engineering students then our results will not be accurate.

We have to work out the relative percentage of each group at a university e. Uses people from target population available at the time and willing to take part. It is based on convenience. An opportunity sample is obtained by asking members of the population of interest if they would take part in your research. An example would be selecting a sample of students from those coming out of the library.

Chooses subjects in a systematic i. To take a systematic sample, you list all the members of the population, and then decided upon a sample you would like. By dividing the number of people in the population by the number of people you want in your sample, you get a number we will call n. If you take every nth name, you will get a systematic sample of the correct size. If, for example, you wanted to sample children from a school of 1,, you would take every 10th name.

This depends on several factors; the size of the target population is important. If the target population is very large e. If the target population is much smaller, then the sample can be smaller but still be representative. There must be enough participants to make the sample representative of the target population. McLeod, S. Sampling methods. Simply Psychology. Toggle navigation. The target population is the total group of individuals from which the sample might be drawn.

A sample is the group of people who take part in the investigation. Generalisability refers to the extent to which we can apply the findings of our research to the target population we are interested in. The Purpose of Sampling The Purpose of Sampling In psychological research we are interested in learning about large groups of people who all have something in common.

How to reference this article: How to reference this article: McLeod, S. Back to top.

Sampling methods in Clinical Research; an Educational Review

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Published on September 19, by Shona McCombes. Revised on February 15, 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.

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.

Methods of sampling from a population

Published on September 19, by Shona McCombes. Revised on February 25, Instead, you select a sample.

CHAPTER FOUR SAMPLING DESIGN Lecture Plan

Sampling is a fundamental part of statistics. Samples are collected to achieve an understanding of a population because it is typically not feasible to observe all members of the population. The goal is to collect samples that provide an accurate representation of the population. Constraints on time and money dictate that the sampling effort must be efficient. More samples are needed to characterize the nature of highly variable populations than less variable populations.

Sign in. Sampling helps a lot in research. If anything goes wrong with your sample then it will be directly reflected in the final result. There are lot of techniques which help us to gather sample depending upon the need and situation.

Learning Skills:. Subscribe to our FREE newsletter and start improving your life in just 5 minutes a day. When you collect any sort of data, especially quantitative data , whether observational, through surveys or from secondary data, you need to decide which data to collect and from whom. There are a variety of ways to select your sample, and to make sure that it gives you results that will be reliable and credible. Ideally, research would collect information from every single member of the population that you are studying.


PDF | Concept of Sampling: Population, Sample, Sampling, Sampling Unit, Sampling Frame, Sampling Survey, Statistic, Parameter, Target.


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  3. EsaГє B.

    It would normally be impractical to study a whole population, for example when doing a questionnaire survey.

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