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Topic: Nonprobability sampling

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Cluster sampling

Systematic sampling

Stratified sampling

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	Nonprobability sampling - Wikipedia, the free encyclopedia
		Sampling is the use of a subset of the population to represent the whole population.
		Nonprobability sampling techniques cannot be used to infer from the sample to the general population.
		The samples in such surveys should be treated as non-probability samples of the population, and the validity of the estimates of parameters based on them unknown.
	en.wikipedia.org /wiki/Nonprobability_sampling (372 words)

	AORN Online: Journal: October 1997: Research Corner (Site not responding. Last check: 2007-11-02)
		Regardless of the probability sampling methods used, the goals are to obtain study samples that are most representative of the populations of interest and to eliminate conscious or subconscious biases that may occur when selecting samples.
		In nonprobability sampling, there is an inherent risk of sampling bias because the populations of interest may not be represented accurately.
		Quota sampling helps ensure that adequate numbers of subgroups that may be underrepresented in convenience samples (eg, ethnic groups, elderly patients, children, underserved populations, the poor) are included in the study sample.
	www.aorn.org /journal/research/rc1097.htm (1315 words)

	Introduction to Sampling
		With nonprobability sampling, in contrast, population elements are selected on the basis of their availability (e.g., because they volunteered) or because of the researcher's personal judgment that they are representative.
		Samples are evaluated primarily according to the procedures by which they were selected rather than by their final composition or size.
		Studies with such samples are useful primarily for documenting that a particular characteristic or phenomenon occurs within a given group or, alternatively, demonstrating that not all members of that group manifest a particular trait.
	psychology.ucdavis.edu /rainbow/html/fact_sample.html (2255 words)

	Chapter Summary
		Purposive (or judgmental) sampling occurs when a researcher selects a sample based on her or his own knowledge of the population, its elements, or the nature of the research study.
		A sample is considered representative of the population from which it is selected if the aggregate characteristics of the sample closely approximate those same aggregate characteristics in the population.
		Once the sampling ratio (the proportion of the population) is determined, the researcher simply selects the elements corresponding to the sampling interval (the distance between elements selected), with the first element selected with a table of random numbers.
	www2.hawaii.edu /~igber197/Ch7Summary.htm (1217 words)

	Survey Sampling Methods
		The sample reflects the characteristics of the population from which it is drawn.
		Sampling error is the degree to which a sample might differ from the population.
		Quota sampling is the nonprobability equivalent of stratified sampling.
	www.statpac.com /surveys/sampling.htm (742 words)

	RESEARCH FORUM--The Research Sample, Part I: Sampling - Journal of Prosthetics and Orthotics, 1995 \| American Academy ...
		Cluster sampling is a method used to enable random sampling to occur while limiting the time and costs that would otherwise be required to sample from either a very large population or one that is geographically diverse (1,2,4,5).
		With nonprobability sampling it is unlikely that the population selected will have the correct proportions because all members of the population do not have an equal chance of being selected.
		The sampling process must be defined well ahead of subject selection whether it be a random (probability) or nonrandom (nonprobability) approach, and the researchers must adhere to a specific technique for recruitment appropriate for that approach.
	www.oandp.org /jpo/library/1995_03_105.asp (4955 words)

	Module 3: Sampling
		It is desirable that the sample be representative of the population.
		Simple random sampling is a technique where we select a group of subjects (a sample) for the study from a larger group (a population).
		When we sample a population with several strata, we generally require that the numbers of individuals in each stratum be in proportion to their percentage in the population.
	polaris.umuc.edu /~melgin/admn638/lect/mod3.htm (1601 words)

	FAQ - Sampling - About Us - Press Ganey Associates, Inc.
		Sampling is the act, process, or technique of selecting a representative subset of the population to determine characteristics of the whole population.
		In nonprobability sampling, the degree to which a sample differs from the population is unknown, and sampling error cannot be determined.
		Whether you use probability or nonprobability sampling methods (which you shouldn’t), resulting samples may be classified as either proportional or nonproportional based on how you determine the quotas or the numbers of individuals to be sampled for each strata.
	www.pressganey.com /about_us/FAQs/FAQ_sampling.php (3157 words)

	Sampling Terminology (Site not responding. Last check: 2007-11-02)
		Random sampling is when each member of the population has an equal chance of being selected to be part of the sample.
		The number of clusters (schools) needed equals the desired sample size (500) divided by the average size of a cluster (50), therefore, the number of schools needed is 500 divided by 50 = 10.
		In educational research/settings, convenience sampling is used widely as a major source of samplingand is major source of sampling bias in research.
	www.uncp.edu /home/baker/edn566sp00/notes/sampling/sample.htm (1420 words)

	Chapter 8 Social Research Methods W
		Sampling Ratio: The number of cases in the sample divided by the number of cases in the population or the sampling frame, or the proportion of the population in the sample.
		A researcher develops an accurate sampling frame, selects elements from the sampling frame according to a mathematically random procedure, and then locates the exact element that was selected for inclusion in the sample.
		A type of random sample that uses multiple stages and is often used to cover wide geographic areas in which aggregated units are randomly selected then samples are drawn from the sampled aggregated units, or clusters.
	www.ucalgary.ca /~bartlett/sampling.html (2307 words)

	sampling (Site not responding. Last check: 2007-11-02)
		Sampling is the process of selecting representative units of a population for study in a research investigation.
		Sample size: the number of subjects and representativeness of the sample are not the focus of subject selection, but rather, subject selection depends most on the richness of information that can be obtained from any given subject.
		If maximum variation is sought in the sample, the researcher may need a sample of 20 to 50 individuals to capture all of the variation sought in the study.
	ruby.fgcu.edu /courses/sbevins/50065/sampling.html (1728 words)

	SURVEY OF EASTERN U.S. FARMWORKER HOUSING; nonprobability sampling
		While probability sampling is preferable in survey work, collecting a nonprobability sample is often necessary due to the nature of the population under study.
		Nonprobability sampling is often the only recourse for researchers interested in gathering information on populations that are difficult to define, locate or recruit.
		Nonprobability sampling has some limitations in generalizing from the data obtained, and is subject to a number of areas of potential bias in the data collection process.
	www.ruralhome.org /pubs/farmworker/meager/appd.htm (1470 words)

	Class 8 :: Populations and Samples (Site not responding. Last check: 2007-11-02)
		Use random sampling, which means that every element (member) of a population has an equal probability (greater than zero probability) of being selected for the study sample.
		Quota sampling is convenience sampling with an added strategy to ensure inclusion of underrepresented subgroups of the population (women, the disadvantaged, and other minority groups).
		Quota sampling increases the representativeness of the sample.
	nursing.unc.edu /modules/nsg_research/pop_sample/topic2.html (192 words)

	Sampling Lectures 2003
		All sampling operates within a matrix of cost considerations, and usually the researcher is under funding constraints that lead to as small as sample size as can be tolerated based on the possible error.
		The distribution of sample statistics is assumed to be distributed normally, but the mean of the sample distribution is not necessarily the population mean.
		Sampling theory is based on simple random sampling but few general population surveys use simple random sampling.
	www.indiana.edu /~survmeth/sampling_lecs_03.htm (3485 words)

	Nonprobability Sampling (Site not responding. Last check: 2007-11-02)
		The difference between nonprobability and probability sampling is that nonprobability sampling does not involve random selection and probability sampling does.
		With nonprobability samples, we may or may not represent the population well, and it will often be hard for us to know how well we've done so.
		This method is the nonprobabilistic analogue of stratified random sampling in that it is typically used to assure that smaller groups are adequately represented in your sample.
	www.socialresearchmethods.net /kb/sampnon.htm (1483 words)

	[No title] (Site not responding. Last check: 2007-11-02)
		The chief criterion of the quality of a sample is the degree to which it is representative -- the extent to which the characteristics of the sample are the same as those of the population from which it was selected.
		Purposive sampling is a type of nonprobability sampling method in which the researcher uses his or her own judgment in the selection of sample members.
		The representativeness of a quota sampling depends in large part on the accuracy of the quota matrix as a reflection of the characteristics of the population.
	www.soc.umn.edu /~xshu/lect11.htm (613 words)

	[No title]
		A nonprobability sample is one in which the probability of selecting any sampling element is [ ] known.
		] sampling is a nonprobability technique useful when you can only identify a few members of a target public directly, but members of the target public are likely to know others in that public.
		Probability samples are drawn in such a way that the probability of selecting any particular sampling element is known.
	www.wsu.edu /~moonlee/pr412handout6.html (550 words)

	Research Methods Handout, 5-B (Site not responding. Last check: 2007-11-02)
		Nonprobability sampling plans are all those which do not meet the requirements of probability sampling; they result in samples in which all elements do not have an equal chance of selection.
		Judgmental sampling - (this is a little confusing, as the text uses the term purposive sampling in discussing this type; I am reserving that term for a different type, see 5.
		Example: selection of one-half of the clients in an agency which you know to be representative of the population based on their demographic and situational characteristics.
	www.mtsu.edu /~jsanborn/resmeth/rmhg5b.htm (342 words)

	Chapter 7 – Sampling
		Useful for collecting data on a group for whom generating a “sampling frame” would be impossible or difficult.
		A sample is representative if the aggregate characteristics of the sample closely approximate those of the entire population
		Term used in sampling that refers to the unit about which information is collected (usually analogous to unit of analysis).
	www.humboldt.edu /~mv23/chapter7.htm (893 words)

	Sampling (Site not responding. Last check: 2007-11-02)
		Sampling is the process of selecting units (e.g., people, organizations) from a population of interest so that by studying the sample we may fairly generalize our results back to the population from which they were chosen.
		Let's begin by covering some of the key terms in sampling like "population" and "sampling frame." Then, because some types of sampling rely upon quantitative models, we'll talk about some of the statistical terms used in sampling.
		Finally, we'll discuss the major distinction between probability and Nonprobability sampling methods and work through the major types in each.
	www.socialresearchmethods.net /kb/sampling.htm (111 words)

	Sampling Terminology Review
		Nonprobability sampling in wich the researcher selects groups of subjects.
		Nonprobablity sampling in which the researhcer selects subjects that have prespecified characteristics.
		Population is divided into strata (subpopulations) on the basis of some variable, then a simple random sample is drawn from each strata.
	web.indstate.edu /mary/N633/samplingquiz.htm (229 words)

	quiz5
		Nonprobability sampling in which the researcher selects groups of subjects.
		Nonprobability sampling in which the researcher selects subjects that have prespecified characteristics.
		Nonprobability sampling in which subjects selected first help recruit other subjects, who then also recruit other subjects.
	web.indstate.edu /mary/N633/quiz5.html (239 words)

	Sampling (statistics) - Wikipedia, the free encyclopedia
		For example, in an opinion poll, possible sampling frames include:
		For example, in simple random sampling, each element has an equal probability of being selected.
		It is important that the first name chosen is not simply the first in the list, but is chosen to be (say) the 7th, where 7 is a random integer in the range 1,...,10-1.
	en.wikipedia.org /wiki/Sampling_(statistics) (2804 words)

	Amazon.com: "nonprobability sampling": Key Phrase page (Site not responding. Last check: 2007-11-02)
		Sample Selection Approaches Approaches to sample selection fall into two broad categories: probability and nonprobability sampling.
		For further discussion of cut-off sampling and other nonprobability sampling designs, the reader is referred to Section 14.4.
		The sample is restricted to a part of the population that is readily accessible.
	www.amazon.com /phrase/nonprobability-sampling (507 words)

	Nonprobability Sampling (Site not responding. Last check: 2007-11-02)
		n non-probability sampling, the sample is selected in such a way that the chance of being selected of each unit within the population or universe is unknown.
		As a result, there are no statistical techniques that allow for the measurement of sampling error, and therefore it is not appropriate to project the sample characteristics to the population.
		In spite of this significant shortcoming, non-probability sampling is very popular in hospitality and tourism research for quantitative research
	www.ryerson.ca /~mjoppe/ResearchProcess/NonprobabilitySampling.htm (109 words)

	Chapter 10: Population and Sampling
		Eligibility criteria are used to select the sample from the population
		Random sampling -selection of a sample from the population
		Random assignment- Unbiased assigning of subjects from a sample into groups in an experimental study
	personal.uncc.edu /lmoore/nurs3200/sampling6.htm (202 words)

	Using Probability vs. Nonprobability Sampling to Identify Hard-to-Access Participants for Health-Related Research: ...
		Using Probability vs. Nonprobability Sampling to Identify Hard-to-Access Participants for Health-Related Research: Costs and Contrasts -- Feild et al.
		Using Probability vs. Nonprobability Sampling to Identify Hard-to-Access Participants for Health-Related Research
		nonprobability sample were more likely to be White.
	jah.sagepub.com /cgi/content/abstract/18/4/565?rss=1 (213 words)

	Amazon.com: "nonprobability sampling methods": Key Phrase page (Site not responding. Last check: 2007-11-02)
		See all pages with references to nonprobability sampling methods.
		Nonprobability Sampling Methods Availability Sampling Quota Sampling Purposive Sampling Snowball...
		Random Sampling Stratified Random Sampling Cluster Sampling Nonprobability Sampling Methods Availability Sampling...
	www.amazon.com /phrase/nonprobability-sampling-methods (429 words)

	Nonprobability Sampling (Site not responding. Last check: 2007-11-02)
		Early members identify and refer other people who meet the eligibility criteria
		Researcher uses knowledge about the population to build representativeness (to ensure that diverse segments are represented in the sample
		Researcher’s knowledge about the population used to handpick the cases to be included in the sample
	classweb.gmu.edu /rfeeg/nurs453/Lecture7/sld006.htm (61 words)

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