what is sampling theory in nursing research

The total 75 study patients [sample] out of the 281 were selected by random sampling method from the patients presenting orders [sampling frame] and evenly divided into three groups; a control group, a foot and hand massage group, and a foot massage group, each of which included 25 patients. Because some patients accepted the intervention before the operation, but changed their mind after the operation (3 patients in total), not all patients participated in the study. (Degirmen et al., 2010, p. 154). Table 15-2 is useful only if the population number is less than 100. Non-probability sampling involves non-random selection based on convenience or other criteria, allowing you to easily collect data. Nonprobability Sampling Methods For systematic sampling to be considered probability sampling, the initial starting point of the sample (the fourth person in this example) is chosen at random. Please try again soon. The researcher, who has a vested interest in the study, could (consciously or unconsciously) select subjects whose conditions or behaviors are consistent with the study hypothesis. Sampling theory can be considered biased since the researcher is picking the population group they want to study. With a stratified random sample, you could use a smaller sample size to achieve the same degree of representativeness as a large sample acquired through simple random sampling. Systematic variation can also occur in studies with high sample attrition. maintain their nursing identity and further their efforts for developing a nursing specialty. In quantitative, intervention, and outcomes research, the findings from a study are generalized first to the accessible population and then, if appropriate, more abstractly to the target population. All rights reserved. A refusal rate is the number and percentage of subjects who declined to participate in the study. Systematic sampling Because of space restrictions, this editorial focuses on the randomised controlled trial (RCT) as an example of quantitative research,and grounded theory as an exampleofqualitativeresearch . As the sample size increases, the sample mean is also more likely to have a value similar to that of the population mean. High refusal rates to participate in a study have been linked to individuals with serious physical and emotional illnesses, low socioeconomic status, and weak social networks (Neumark, Stommel, Given, & Given, 2001). To study the prevalence of elder abuse in nursing homes, Schiamberg and colleagues conducted a random digit-dialing telephone survey of noninstitutionalized adults in Michigan who have a relative in long-term care. 63 These researchers obtained their sample using a simple random sampling method that is described in the following excerpt from their study. Similar to stratified random sampling, cluster random sampling uses natural geographic and organizational clusters of potential research participants to create a sampling frame.2 For example, in exploring work satisfaction among clinical nurses using a cluster sampling methodology, the researcher would randomly select cities from which to draw the sample, then randomly select hospitals from within each city, and finally randomly assign nurses from within each hospital to participate in the study. 19 Exclusion criteria tend to increase the systematic bias in the sample and increase the sampling error. to maintaining your privacy and will not share your personal information without A study might have inclusion or exclusion sampling criteria (or both). Using random sampling, the researcher cannot decide that person X would be a better subject for the study than person Y. Researchers have adopted the assumptions of sampling theory identified for the census surveys and incorporated them within the research process (Thompson, 2002). The acceptance rate is calculated by dividing the number of potential subjects who agree to participate in a study by the number of potential subjects who meet sampling criteria and multiplying the result by 100%. Within the hospitals, nursing units might be randomly selected. That said, the researcher must be alert to a number of methodological and ethical pitfalls associated with recruitment and retention.18 Recruitment techniques such as monetary incentives for participation may bias the study outcome; and the extent that subjects systematically discontinue participation in the study may disrupt the balance of the study sample, creating threats to generalizability and study validity. One question that arises in relation to stratification is whether each stratum should have equivalent numbers of subjects in the sample (termed disproportionate sampling) or whether the numbers of subjects should be selected in proportion to their occurrence in the population (termed proportionate sampling). For example, if your study examines attitudes toward acquired immunodeficiency syndrome (AIDS), the sample should represent the distribution of attitudes toward AIDS that exists in the specified population. A sampling method is similar to a design; it is not specific to a study. Subjects within each stratum are expected to be more similar (homogeneous) in relation to the study variables than they are to be similar to subjects in other strata or the total sample. These values do not vary randomly around the population mean. While less expensive, nonprobability sampling techniques are prone to selection bias and often do not produce a sample that fully represents the target population. Capili B. Professional Development, Leadership and Scholarship, Professional Partners Supporting Diverse Family Caregivers Across Settings, Supporting Family Caregivers: No Longer Home Alone, Nurse Faculty Scholars / AJN Mentored Writing Award. Random sampling increases the extent to which the sample is representative of the target population. Understanding the differences in sampling techniques may aid nurses in effective appraisal of research literature and provide a reference pointfor nurses who engage in cardiovascular research. Sampling error limits generalizability and research accuracy (validity) by introducing bias into the study. For example, a narrow definition of the accessible population reduces the ability to generalize from the study sample to the target population and diminishes the meaningfulness of the findings. The likelihood is increased that the sample is representative of the target population and the results are an accurate reflection of reality. Sampling Theory and Generalizability in Nursing Research Sampling theory refers to the study of the relationships that exist between a population and the samples which are drawn from a population. However, some researchers still use a table of random numbers to select a random sample. National Center for Biotechnology Information, Lister Hill National Center for Biomedical Communications, Agency for Healthcare Research and Quality, Centers for Disease Control and Prevention, Robert Wood Johnson Foundation County Health Rankings & Roadmaps, Centers for Medicare and Medicaid Services. Sampling error is usually larger with small samples and decreases as the sample size increases. In the first stage, 339 primary sampling units were selected from about 1,900 area sampling units representing counties, groups of adjacent counties, or metropolitan areas covering the 50 states and the District of Columbia [1st stage cluster sampling]. Sampling A sampling method is similar to a design; it is not specific to a study. However, some researchers still use a table of random numbers to select a random sample. The number touched is the starting place. For example, one could conduct a study in which the defined population was all living recipients of heart and lung transplants. If the sampling frame is small, the researcher can write names on slips of paper, place the names in a container, mix well, and draw out one at a time until the desired sample size has been reached. The series is designed to give nurses the knowledge and skills they need to participate in research, step by step. The subjects were evenly divided with 25 in each group, but the researchers do not indicate if the assignment to groups was random or based on the convenience of the subjects or researchers. If five subjects are to be selected from a population of 100 and the researcher decides to go across the column to the right, the subject numbers chosen are 58, 25, 15, 55, and 38. The accuracy with which the population parameters have been estimated within a study is referred to as precision. The sample must be randomly selected from the sampling frame. Would you like email updates of new search results? Obese individuals who choose to enter a program to lose weight may differ from obese individuals who do not enter a program. Because this is a quasi-experimental study that examined the impact of the treatment on the dependent or outcome variables, the increased controls imposed by the sampling criteria strengthened the likelihood that the study outcomes were caused by the treatment and not by extraneous variables. The refusal rate is calculated by dividing the number of potential subjects refusing to participate by the number of potential subjects meeting sampling criteria and multiplying the results by 100%. sharing sensitive information, make sure youre on a federal It is tempting to exclude uncooperative or assertive individuals. All the values in the sample may tend to be higher or lower than the mean of the population (Thompson, 2002). Twiss et al. Each member of the sampling frame has only one chance of being chosen for inclusion in the study sample.4 For example, suppose a nurse researcher is interested in workplace satisfaction among the 200 medicalsurgical nurses within a health care system. To use a table of random numbers, the researcher places a pencil or a finger on the table with the eyes closed. The following sections describe the different types of probability and nonprobability sampling methods most commonly used in quantitative, qualitative, outcomes, and intervention research in nursing. The site is secure. These criteria ensure a large target population of. Good arguments exist for both approaches. Am J Nurs. While recruitment and retention of research subjects can be one of the most challenging aspects of sampling, strategic messaging, relationship building, and financial incentives may facilitate the process. The sampling criteria determine the target population, and the sample is selected from the accessible population within the target population (see Figure 15-1). Systematic variation can also occur in studies with high sample attrition. Am J Nurs 2021;121(1):647. However, tables are available for larger populations, such as the random numbers table provided in the online resources for this textbook or the Thompson (2002, pp. Stigmatization and mental health in a diverse sample of transgender women. The only nursing research and theory book with primary works by the original theorists. In most instances, television, newspapers, and advertisements do not explain their sampling techniques. The difference between a sample statistic and a population parameter is called the sampling error (Figure 15-2). Validity and reliability are two statistical properties used to evaluate the quality of research instruments (Anastasi, 1986). (2009) identified specific inclusion and exclusion sampling criteria to designate the subjects in the target population precisely. The higher the refusal rate, the less the sample is representative of the target population. A sampling method is the process of selecting a group of people, events, behaviors, or other elements that represent the population being studied. Subjects and the care they receive in research centers are different from patients and the care they receive in community clinics, public hospitals, veterans hospitals, and rural health clinics. Quantitative, outcomes, and intervention research apply a variety of probability and nonprobability sampling methods. There are many ways to achieve random selection, such as with the use of a computer, a random numbers table, drawing names out of a hat, or a roulette wheel. Grounded theory (GT) is a research method concerned with the generation of theory,1 which is 'grounded' in data that has been systematically collected and analysed.2 It is used to uncover such things as social relationships and behaviours of groups, known as social processes.3 It was developed in California, USA by Glaser and Strauss during their study'Awareness of Dying'.1 It is a . This article reviews probability and non-probability sampling methods, lists and defines specific sampling techniques, and provides pros and cons for consideration. Systematic bias increases as the subjects refusal rate increases. AJN The American Journal of Nursing121(3):53-57, March 2021. Accessible potential research participants who meet the research subject selection criteria create the sampling frame from which the study sample is drawn. . Systematic variation or bias is most likely to occur when the sampling process is not random. I think this all sounds like a pretty standard way to . Careers. As further names are drawn, the probability of being selected decreases. (2009) conducted a quasi-experimental study to examine the effects of strength and weight training (ST) exercises on muscle strength, balance, and falls of breast cancer survivors (BCSs) with bone loss (population). The sampling plan of a research study is presented in the methods section of a research proposal or research article. An accessible population is the portion of the target population to which the researchers have reasonable access. This situation usually occurs because of an interaction of the systematic bias with the treatment. Krishnasamy M, Hassan H, Jewell C, Moravski I, Lewin T. Healthcare (Basel). The following excerpt from this study describes the sampling method used to obtain the final sample of 1536 providers (833 NPs and 689 PAs). In general, the larger the sample size, the smaller the sampling error. Age limitations are often specified, such as adults 18 years and older. Application of simple random sampling and the attrition of only three (4%) subjects from the study seem to provide a sample representative of the target population. The study was conducted in obstetric intensive care units and services of all the public and university hospitals in the province of Eskisehir, Turkey. During the 4 month study, 281 patients attended for the cesarean operations to the obstetric intensive care units and services of all hospitals concerned [target population and settings]. The development of a thoughtful sampling plan is essential to support the validity of nursing research. 16. It is especially important that the sample be representative in relation to the variables you are studying and to other factors that may influence the study variables. 72 High refusal rates to participate in a study have been linked to individuals with serious physical and emotional illnesses, low socioeconomic status, and weak social networks (Neumark, Stommel, Given, & Given, 2001). (2009) found significant improvement in muscle strength and balance for the treatment group but no significant difference in the number of falls between the treatment and comparison groups. The subgroup that you are going to study, intended to be representative of the population at large for the characteristics of interest. However, even in a random sample, systematic variation can occur if potential subjects decline participation. In the aforementioned situation, if proportions are used and the sample size is 100, the study would include only five Asians, hardly enough to be representative. 8600 Rockville Pike Selecting the sample for a research study. The study was conducted at a large urban hospital in the U.S. northeast region that is a nongovernment, not-for-profit, general medical and surgical major teaching hospital. Imagine trying to arrange personal meetings with 100 people, each in a different part of the United States. The chapter concludes with a discussion of the process for recruiting and retaining subjects or participants for study samples in various settings. representative in relation to the variables you are studying and to other factors that may influence the study variables. The higher the refusal rate, the less the sample is representative of the target population. The sample was selected from the national lists provided by Medical Marketing Services, an independently owned organization that manages medical industry lists (www.mmslists.com/main.asp). If the method of selecting subjects produces a sample with a systematic bias, increasing the sample size would not decrease the sampling error. Data collection continues until theoretical saturation is achieved.12 For example, as the nurse researcher begins to understand more about the context of early opioid initiation in the study example, the researcher might choose to intentionally sample participants with similar experiences, such as a history of adverse childhood events. When elements are persons, they are usually referred to as subjects or research participants or informants (see Figure 15-1). Unauthorized use of these marks is strictly prohibited. TABLE 15-1 Capili B. Contact Us, Copyright The Board of Regents of the University of Wisconsin System, Library Research Guides - University of Wisconsin Ebling Library. Probability sampling methods are most commonly applied in quantitative, outcomes, and intervention research. A numerical value of a population is called a parameter. Each column will present the concepts that underpin evidence-based practice-from research design to data interpretation. The sample is obtained from the accessible population by a particular sampling method, such as simple random sampling. Systematic variation or bias is most likely to occur when the sampling process is not random. (2009) identified specific inclusion and exclusion sampling criteria to designate the subjects in the target population precisely. Nurs Health Sci. Population, sample, and subject selected for a study. Palinkas LA, et al. Each approach offers distinct advantages and disadvantages and must be considered critically. https://researchguides.library.wisc.edu/nursing, Types of Research within Qualitative and Quantitative, Independent Variable VS Dependent Variable, Nursing Scope & Standards of Practice, 4th Ed, Find Instruments, Measurements, and Tools. The difference is random because the value of each subject is likely to vary in a different direction. For a sample to be representative, it must be similar to the target population in as many ways as possible. Again, these units could be people, events, or other subjects of interest. 43 The second situation is in cases in which the individual elements making up the population are unknown, preventing the development of a sampling frame. However, it has some disadvantages. Non-probability sampling does not involve random selection and so cannot rely on probability theory to ensure that it is representative of the population of interest. In creating the study design, researchers choose between a probability and a nonprobability sampling strategy. Sample Representativeness However, in quasi-experimental or experimental studies, the primary purpose of sampling criteria is to limit the effect of extraneous variables on the particular interaction between the independent and dependent variables. It is from the sample that data is collected in the course of a study, and because that sample is representative of the population, the results can be generalized to the population in a scientific study. While probability sampling minimizes selection bias and enhances generalizability of a study, it is often associated with sizable time and financial costs, particularly if the study sample is large. However, some of the outcomes are more valid than others, partly because of the sampling techniques used. The retention rate is calculated by dividing the number of subjects completing the study by the initial sample size and multiplying by 100%. The study has a strong response rate of 50.6% for a mailed questionnaire, and the researchers identified why certain respondents were disqualified. That said, nonprobability sampling has important drawbacks. Sometimes researchers provide an acceptance rate, or the number and percentage of the subjects who agree to participate in a study, rather than a refusal rate. However, even in a random sample, systematic variation can occur if potential subjects decline participation. Persons who are able to participate fully in the procedure for obtaining informed consent are often selected as subjects. Thus, persons who are legally or mentally incompetent, terminally ill, or confined to an institution are more difficult to access as subjects (see Chapter 9). 12. The retention rates for both groups were very strong and comparable (treatment group 89% and comparison group 90%). Degirmen, Ozerdogan, Sayiner, Kosgeroglu, and Ayranci (2010, p. 153) conducted a pretest-posttest randomized controlled experimental study to determine the effect of hand and foot massage and foot massage only interventions on the postoperative pain of women who had a cesarean operation. 2020 Oct;120(10):41-44. doi: 10.1097/01.NAJ.0000718644.96765.b3. Table 15-2 shows a section from a random numbers table. 66 Twiss et al. To achieve these goals, researchers need to understand the techniques of sampling and the reasoning behind them. Essentials of epidemiology in public health. Unauthorized use of these marks is strictly prohibited. 750 Highland Ave, Madison, WI 53705-2221 In a second step, primary sampling units were partitioned into substrata (up to 21) based on concentrations of African American and Hispanic populations [2nd stage cluster sampling]. 14-15) sampling text. Abstract. Exclusion criteria limit true randomness. 39 This correlation can cause a decrease in precision and an increase in sampling error. Alexa Colgrove Curtis is assistant dean of graduate nursing and director of the MPHDNP dual degree program and Courtney Keeler is an associate professor, both at the University of San Francisco School of Nursing and Health Professions. For example, if a study had a sample size of 160, and 40 people withdrew from the study, the attrition rate would be 25%. Sampling strategies have been devised to accomplish these three tasks and to optimize sample selection. psychomotor, and affective changes. Probability sampling assumes both random selection of participants and sampling independence.6Sampling independence requires two conditions: the selection of one participant must not impact or affect the equal chance of selection of other participants, and selection probability should not be influenced by shared characteristics among prospective participants.6Random selection of participants from the sampling frame can be performed using a number of mechanisms, including a random digit-dialing telephone survey, a computerized randomization tool, a spreadsheet randomization function, a table of random numbers, or by manually drawing from a hat or flipping a coin. If potential subjects have diminished autonomy or are unable to give informed consent, consent must be obtained from their legal representatives. For example, numbers are assigned to medical records, organizational memberships, and professional licenses. Federal government websites often end in .gov or .mil. Accessibility Selection bias and sampling plan. Random sampling is the best method for ensuring that a sample is representative of the larger population. (2009) found significant improvement in muscle strength and balance for the treatment group but no significant difference in the number of falls between the treatment and comparison groups. In systematic random sampling (SYS), units are selected from the frame at regular intervals, and a sampling interval and a random start are required. Freedman D, et al. Cluster sampling is used in two situations. Studies conducted in private hospitals usually exclude poor patients, and other settings could exclude elderly or undereducated patients. In large population sets, elements may already have assigned numbers. All samples with human subjects must be volunteer samples, which includes individuals willing to participate in the study, to protect the rights of the individuals (Fawcett & Garity, 2009). It's a way of measuring how much a person's personality is similar to yours. States, cities, institutions, or organizations are selected randomly as units from which to obtain elements for the sample. In: 5. Today, federal funding for research is strongly linked to including these populations in studies. In this research column, we provide an introduction to these key sampling techniques and draw on examples from the cardiovascular research. What Is Sampling Theory in Nursing Research? Probability (Random) Sampling Methods Variables commonly used for stratification are age, gender, ethnicity, socioeconomic status, diagnosis, geographical region, type of institution, type of care, care provider, and site of care. The opposite of the attrition rate is the retention rate, or the number and percentage of subjects completing the study. Sampling involves selecting a group of people, events, behaviors, or other elements with which to conduct a study. Using random sampling, the researcher cannot decide that person X would be a better subject for the study than person Y. Fundamentals of mathematical statistics. For each person in the target or accessible population to have an opportunity to be selected for the sample, each person in the population must be identified. The individual units of the population and sample are called elements.

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what is sampling theory in nursing research

what is sampling theory in nursing research