what is sampling theory in nursing research

2010 Sep 1;12(3):369-74. doi: 10.1111/j.1442-2018.2010.00541.x. The comparison group retention was 113 women with a retention rate of 90% (113 125 = 90.4% = 90%). Most of the variation from the mean is in the same direction; it is systematic. The sample is most like the target population if the attrition rate is low (<10% to 20%) and the subjects withdrawing from the study are similar to the subjects completing the study. In stratified random sampling, a population is first categorized into specific, nonoverlapping groups (or strata); random samples are then taken from within each group (see Figure 1).5 Stratified sampling facilitates the representation of important participant characteristics in the study sample and improves data collection from underrepresented subgroups. A self-administered questionnaire was mailed to an initial stratified random sample [sampling method] of 3,900 NPs and PAs practicing in the United States. Sample attrition should be reported in the published study to determine if the final sample represents the target population. Stratification ensures that all levels of the identified variable, in this example age, are adequately represented in the sample. Probability sampling methods are most commonly applied in quantitative, outcomes, and intervention research. AJN The American Journal of Nursing121(3):53-57, March 2021. Many of these studies use data available in large databases, such as the census data or other government-maintained databases. The extent of the difference is the sampling error (see Figure 15-2). Patient volume, staffing, and workload in relation to risk-adjusted outcomes in a random stratified sample of UK neonatal intensive care units: a prospective evaluation. 93 Another technique is to assign a number to each name in the sampling frame. Bethesda, MD 20894, Web Policies Burlington, MA: Jones and Bartlett Learning; 2020. In any case, it is rarely possible to obtain a purely random sample for nursing studies because of informed consent requirements. In the example mentioned earlier, 200 potential subjects met the sampling criteria; 160 agreed to participate in the study, and 40 refused. 14. Patient satisfaction with triage nursing care in Hong Kong. Quantitative, outcomes, and intervention research Sampling, data collection, and data analysis. These sampling criteria probably were narrowly defined by the researchers to promote the selection of a homogeneous sample of postmenopausal BCSs with bone loss. However, the study would have been strengthened by a discussion of the process for random sampling and a clarification of how the subjects were assigned to groups. Sampling error is usually larger with small samples and decreases as the sample size increases. All rights reserved. 39 This correlation can cause a decrease in precision and an increase in sampling error. Would you like email updates of new search results? FOIA Table 15-2 shows a section from a random numbers table. 33 It is used to measure a concept of interest. Today, federal funding for research is strongly linked to including these populations in studies. However, the sample was a great strength of this study and appeared to represent the target population of NPs and PAs currently practicing in primary care in the United States. Attritionrate=40(numberwithdrawing)160(samplesize)=0.25100%=25% In addition, a sample must represent the demographic characteristics, such as age, gender, ethnicity, income, and education, which often influence study variables. These biases are similar to biases that may be encountered in a nonrandom sample (Thompson, 2002). Many of us have preconceived notions about samples and sampling, which we acquired from television commercials, polls of public opinion, market researchers, and newspaper reports of research findings. You might identify broad sampling criteria for a study, such as all adults older than 18 years of age able to read and write English. Djukic, Kovner, Budin, and Norman (2010) studied the effect of nurses perceived physical work environment on their job satisfaction and described their sampling frame in the following excerpt. Systematic bias increases as the subjects refusal rate increases. Cardiovascular nursing research covers a wide array of topics from health services to psychosocial patient experiences. Therefore, the sampling design of the NHIS includes oversampling of minorities. (Fouladbakhsh & Stommel, 2010, pp. The sampling criteria determine the target population, and the sample is selected from the accessible population within the target population (see Figure 15-1). Cutcliffe JR, et al. This study included clearly identified inclusion and exclusion sampling or eligibility criteria that are presented in the following excerpt. 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. (2009) identified specific inclusion and exclusion sampling criteria to designate the subjects in the target population precisely. Sampling theory describes two sampling domains: probability and nonprobability. PMC For example, if the researcher is selecting 10 subjects from a population of 50, the first name has a 1 in 5 chance (10 draws, 50 names), or a 0.2 probability, of being selected. To use a table of random numbers, the researcher places a pencil or a finger on the table with the eyes closed. Sampling theory is the study of the relationship between a given population and portion picked randomly as a representation of the whole population (McNiff & Petrik, 2018). Sampling methodology influences how well the study represents the target population, and thereby affects the generalizability of the study. 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]. (2010) clearly identified their target population as women needing cesarean operations, and the 281 women with presenting orders provided the sampling frame for the study. Sampling Error Sampling Plan Moving the pencil or finger up, down, right, or left, the researcher uses the numbers in order until the desired sample size is obtained. Cluster sampling is used in two situations. In these cases, it is often possible to obtain lists of institutions or organizations with which the elements of interest are associated. 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. Data from subjects associated with the same institution are likely to be correlated and not completely independent. This sampling technique often selects clinical cases or participants that are available around a location (such as hospital), medical records database, Internet site, or customer-membership list. Thus, a study that uses random sampling techniques may have such restrictive sampling criteria that the sample is not truly random. In stratified random sampling, the subjects are randomly selected on the basis of their classification into the selected strata. Representativeness is usually evaluated by comparing the numerical values of the sample (a, The difference between a sample statistic and a population parameter is called the, Systematic variation or bias is most likely to occur when the sampling process is not random. Ebling Library, Health Sciences Learning Center Rodriguez J, et al. Nonprobability sampling. These values do not vary randomly around the population mean. This can be done by random, by convenience or even self-selected. 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 plan defines the process of making the sample selections; sample denotes the selected group of people or elements included in a study. Qualitative researchers use nonprobability sampling to identify constructs of interest within a target population to further theory development. In a study of the relationship between Eating Inventory questionnaire factors (restraint, disinhibition, and hunger) and body adiposity and associated comorbidities (such as diabetes) among a cohort of Czech adults, Hainer and colleagues used quota sampling to provide proportional representation based on gender, age, residential location, education, socioeconomic level, and marital status. Chapter 15 63 Random sampling increases the extent to which the sample is representative of the target population. Sample surveys. Ultimately, researchers hope to make generalizations about the target population (for example, persons in the United States with lung cancer) based on data collected from the study sample (lung cancer patients at a regional oncology center). Stigmatization and mental health in a diverse sample of transgender women. Djukic, Kovner, Budin, and Norman (2010) studied the effect of nurses perceived physical work environment on their job satisfaction and described their sampling frame in the following excerpt. Epub 2017 Nov 2. Exclusion criteria limit true randomness. 2023 Feb 4;11(4):452. doi: 10.3390/healthcare11040452. 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. 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) Good arguments exist for both approaches. and transmitted securely. Federal government websites often end in .gov or .mil. A diagram showing the connection betweenpopulation andsample size. Your message has been successfully sent to your colleague. Nutrients. 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. 8th ed. An official website of the United States government. and transmitted securely. Nonprobability Sampling Methods 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. According to sampling theory, it is impossible to select a sample randomly from a population that cannot be clearly defined. 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. Twiss et al. 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. Random variation is the expected difference in values that occurs when one examines different subjects from the same sample. Selection bias and sampling plan. In some cases, this random selection continues through several stages and is referred to as multistage cluster sampling. The opposite of the attrition rate is the retention rate, or the number and percentage of subjects completing the study. This goal can be accomplished in various ways, limited only by the imagination of the researcher. In a study by the UK Neonatal Staffing Study Group of the association between patient volume, staffing levels, and workload and risk-adjusted outcomes of neonatal mortality and hospital-acquired infections, the sample was stratified into units by patient volume (high, medium, low), pediatrician availability (high and low), and nurse-to-patient ratios (high and low). Women were included if they were 35-77 years of age, had a history of stage 0 (in situ), I, or II breast cancer, a BMD [bone mineral density] T-score of 1.0 or less at any of three sites (hip, spine, forearm), were at least 6 months post breast-cancer treatment and 12 months postmenopausal, resided within 100 miles of one of four research sites (Omaha, Lincoln, Kearney, and Scottsbluff, NE), and had their physicians permission to participate [inclusion sampling criteria]. You may also needUsing Statistics to Determine DifferencesUsing Statistics to Describe VariablesMeasurement ConceptsUsing Statistics to PredictSelecting a Quantitative Research DesignCollecting and Managing DataFrameworksDisseminating Research Findings The sampling component is an important part of the research process that needs to be carefully thought out and clearly described. The sample theory is merely applicable to the random samples. Cluster sampling The sampling plan may use probability (random) sampling methods or nonprobability (nonrandom) sampling methods. The sample of 75 women was randomly selected, but the researchers did not indicate the process for the random selection. Exclusion criteria limit the generalization of the study findings and should be carefully considered before being used in a study. Refusalrate=40(numberrefusing)200(numbermeetingsamplingcriteria)=0.2100%=20% However, random sampling must take place in an accessible population that is representative of the target population. The study by Twiss et al. 3 Sampling decisions are made for the explicit purpose of obtaining the richest possible source of information to answer the research . Representativeness of the sample refers to how well aligned the study sample is to the target population.2 In an ideal setting, a study sample would perfectly mirror the target population; however, this, as we know, is impossible. The use of the term control groupthe group not receiving the treatmentis usually limited to studies using random sampling and random assignment to the treatment and control groups. Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on Google+ (Opens in new window) The study has a strong response rate of 50.6% for a mailed questionnaire, and the researchers identified why certain respondents were disqualified. The target population is the entire set of individuals or elements who meet the sampling criteria, such as women who have experienced a myocardial infarction in the past year. Systematic bias increases as the subjects refusal rate increases. It is applicable only to random samples. representative in relation to the variables you are studying and to other factors that may influence the study variables. 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. For more information, please refer to our Privacy Policy. While the purpose of stratified random sampling is to improve participant representation, the purpose of cluster sampling is to improve sampling efficiency, thus reducing time and cost.3. This site needs JavaScript to work properly. Because it is impossible to know the sampling error exactly, all sampling errors are approximate and are based on a calculation called the standard deviation. The term study or research participant or informant is used in the context of the naturalistic paradigm of qualitative research (Fawcett & Garity, 2009; Munhall, 2012). Sampling decisions have a major impact on the meaning and generalizability of the findings. (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). In this case, mathematically weighting the findings from each stratum can equalize the representation to ensure proportional contributions of each stratum to the total score of the sample. The comparison group retention was 113 women with a retention rate of 90% (113 125 = 90.4% = 90%). Probability sampling is the random selection of elements from the population, where each element of the population has an equal and independent chance of being included in the sample. 2014 Jun;61(3):105-11. doi: 10.6224/JN.61.3.105. The retention rates for both groups were very strong and comparable (treatment group 89% and comparison group 90%). 66 In any case, it is rarely possible to obtain a purely random sample for nursing studies because of informed consent requirements.

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