Sampling - This resource provides a brief overview of sampling and sample size with links to descriptions of purposeful sampling strategies. A Guide to Using Qualitative Research Methodology - The file linked below contains a full description of how to conduct qualitative sampling, including a chart that lists the types of sampling techniques and includes examples.
Sampling Designs in Qualitative Research - The following article discusses sampling designs and ways to make the sampling process more public.
This pin will expire , on Change. This pin never expires. Select an expiration date. About Us Contact Us. Search Community Search Community. Qualitative Sampling Methods The following module describes common methods for collecting qualitative data.
Describe common types of qualitative sampling methodology. Explain the methods typically used in qualitative data collection. Describe how sample size is determined. Purposeful Sampling is the most common sampling strategy. In this type of sampling, participants are selected or sought after based on pre-selected criteria based on the research question.
For example, the study may be attempting to collect data from lymphoma patients in a particular city or county. The sample size may be predetermined or based on theoretical saturation, which is the point at which the newly collected no longer provides additional insights.
Click on the following link for a desciption of types of purposeful sampling: Types of Purposeful Sampling. Quota Sampling is a sampling technique whereby participant quotas are preset prior to sampling. Typically, the researcher is attempting to gather data from a certain number of participants that meet certain characteristics that may include things such as age, sex, class, marital status, HIV status, etc.
Click here for more information on this type of sampling: Snowball Sampling is also known as chain referral sampling. In this method, the participants refer the researcher to others who may be able to potentially contribute or participate in the study.
This method often helps researchers find and recruit participants that may otherwise be hard to reach. For more information, click here: Collecting Qualitative Data from highness In this example, the interactions observed may be biased because the pharmacist does not work on the day observed.
You also miss the clients who obtain their medicines from other sources. Informal drug outlets in communities are often as important as pharmacies as sources of medicines. It is necessary to study interactions at those outlets as well, to get a good impression of the provision of information on drugs. This sampling method aims to select study units which represent a wide range of variation in dimensions of interest.
For example, the researcher may be interested in the reasons that people do not comply with antibiotic prescriptions, and assume that gender and socio-economic status are important background variables. The researcher is afraid to miss men, who are often not at home when researchers visit to conduct semi-structured interviews. Therefore, the researchers decide to conduct interviews during the day and in the evenings, and to ensure that at least 15 men and women are included in the sample.
Maximum variation can also be used as a strategy to select communities in which to do research. In the example, this would imply that the researcher selects one relatively rich and one poor community. Maximum variation sampling is also often used when deciding on which groups to involve in focus group discussions. Remember, the informants participating in each FGD should be relatively homogenous as far as key background variables for the study are concerned. Snowball sampling is perhaps the most common sampling method used in qualitative studies.
The researcher starts by identifying some at least two individuals who are relevant to the study, for example, women with pre-school children in a study on home-treatments in malaria, and then asking them to locate other useful informants, i. The advantage of this method is that one informant refers the researcher to another, so that the researcher has a good introduction for the next interview.
A disadvantage is that the variation in the sample may be limited because it consists of informants who belong to the networks of the index cases. This is why it is important to have at least two different additional entrances in the community. Comparative studies sampling will involve two or more population groups with distinct characteristics. This sampling method is useful in comparative studies that aim to explain problems by establishing which factors are associated with them or cause them.
For example, in a study aimed at understanding why mothers do not use oral rehydration therapy ORT to prevent childhood death in diarrhoea cases, both women who use ORT and those who do not can be sampled and compared. Contrast sampling can also be used in selecting research sites.
For example, when evaluating a health programme, a research site can be selected where according to statistical information the programme has been successful for example, in promoting ORT and where this is not the case.
Comparison can help in analysing which factors contribute to success and which factors constrain programme success. Contrast sampling can also be used to select participants for focus group discussions. Within each group the informants should be relatively homogenous in terms of the important dimensions of the study; but for the different groups you select contrasting cases for example, men and women; younger and older; users and non users.
The qualitative methods presented in Chapter 3 for investigation on drug use include semi-structured interviews and FGDs. How can we sample respondents for these methods? First you need to define whom you want to interview. If you are aiming to get an overview of drug use problems, it is best to select a wide range of individuals. If you are analysing a specific drug use problem, you concentrate on people who have direct experience with the drug use practice that is problematic, and people who are knowledgeable about it.
Snowball sampling is the most common sampling method used in selecting respondents for semi-structured interviews. You can also decide to conduct contrast sampling.
The goal of qualitative research is to provide in-depth understanding and therefore, targets a specific group, type of individual, event or process. To accomplish this goal, qualitative research focus on criterion-based sampling techniques to reach their target group.
Assumptions of qualitative samplingSocial actors are not predictablelike objects. Randomized events are irrelevant to social life. Probability sampling is expensive Therefore and inefficient. Non-probability sampling is the best approach. Types of .
Sampling is a very complex issue in qualitative research as there are many variations of qualitative sampling described in the literature and much confusion and overlapping of types of sampling, particularly in the case of purposeful. Probably the most frequently cited source for a summary of the different varieties of sampling in qualitative research in Michael Patton () Qualitative Research & Evaluation Methods (3rd ed.).
Sampling for Qualitative Research •The aim of the qualitative research is to understand, from within, the subjective reality of the study participants. Mar 01, · A review of the few qualitative research publications that treat sampling issues at greater length (e.g., Depoy and Gitlin ; Miles and Huberman ; Morse ; Ragin and Becker ) identify five major types of nonprobability sampling techniques for qualitative research.