Chapter6Chapter at a GlanceDescribes types of sampling methods and ways to determine which one isappropriate for your programFocuses on one commonly used sampling method: cluster samplingReviews how to determine and calculate the sample size you need for your datacollection activitiesou may choose to seek outside help.Sampling, when done well, is a key aspectof an evaluations credibility.However,sampling can be complicated, especiallywhen evaluating large, complex programs.After reading this chapter, you may want toseek technical assistance to make sure thaty sound.
Experts at localuniversities and research institutes can helpficient sampling schemefor your program evaluation.Types of Sampling MethodsSampling methods fall into two broadcategories: probability, and non-probability.You will need to make a choice aboutwhich type to use.Probability sampling, probabilitysampling methods can be time-consumingy and require a level of skill yourprogram may not possess.
Non-probabilitysampling methods are more flexible, lesscostly and less time-consuming, but giveyou weaker evaluation results.
Probability sampling methods are based onprobability theory, a mathematical conceptbased on accepted statistical principles thaters to the ability to predict the statisticallikelihood that a random event will occur.Probability sampling methods require that:every program element has a chanceof being chosen (note: elements doy a chance),it is possible to calculate theprobability of each element beingrandom chance determines whichelements are chosen.Conversely, non-probability samplingmethods are not based on probabilityy.With these methods, samples arenot chosen by random chance.Thesemethods can include:obtaining a sample of subjects on thebasis of opportunity,using your judgment to choose whatyou think is a representative sample ofer population, orbasing sample selection on referralsfrom other sample subjects.The table below describes specificsampling methods that fall within the twocategories.A Guide to Monitoring and Evaluating Adolescent Reproductive Health ProgramsA Guide to Monitoring and Evaluating Adolescent Reproductive Health Programs A part of a whole selected to represent that whole.The person from whom you will collect data; an element An aggregated group of elements from which you willIn general, informationcollected during a processevaluation will measureprogram-level objectives.Information collectedduring an outcome orimpact evaluation willmeasure population-levelobjectives.hat Sampling Method Is Best?To select the sampling method that is bestfor your needs, you should consider:the time and resources you haveavailable,the size of your program,the indicators you plan to measure,andthe data sources you plan to collectinformation from
1 Systematic Sampling
1 Systematic Sampling Things to know ... † Advantages and disadvantages. This is a sampling method in some sense similar to stratiﬂed random sampling. (jstor.org)
Sampling Methods - Welcome To Www.westfallteam.com
Systematic sampling is another statistical sampling method. In this method, every nth element from the list is selected as the sample, ... (fhi360.org)
The box on the next page summarizes themajor advantages and disadvantages ofprobability and non-probability samplingProbability sampling is preferred formost types of youth programevaluations.If you work with a program that has a targetpopulation of more than 100 youth and aretrying to measure changes in the indicatorsrelated to your program objectives,probability sampling methods will give youmore objective and scientifically defensibleevaluation findings.Non-probabilitysampling methods, while less costly andtime-consuming, may leave you vulnerableto questions about whether your evaluationy reason some programs do not useprobability sampling for their evaluation isbecause they lack the time, resources orexpertise to conduct this type of sampling.Non-probability sampling should beused in certain circumstances.There are some circumstances in whichy not be possibleor preferred:The evaluation of smaller youthprograms:When there are smallnumbers of elements (fewer than 20)being chosen, the key statisticalproperties of probability sampling donot apply.
If you plan to collect datafrom fewer than 20 individuals, a Chapter 6:
SamplingTypes of Sampling MethodsProbability Sampling Methods Elements are chosen at The first element is chosen at The population to be sampled is First, a simple random sample of A sampling frame is defined in advance or sampling.non-probability quota sample that youconsider representative in terms ofimportant characteristics is just aseffective as a probability sample.Some programs work with sub-groupsof youth, such as street children orug users.In these situations, it maybe difficult or impossible for you toconstruct asampling frame, or a list ofall youth who belong to the targetpopulation.Without a sampling frame,you cannot conduct probabilityten the only feasibleoption.When conducting focus groupdiscussions:Trying to assemble arandomly chosen group ofrespondents in a given location toocus groups is difficult.Therefore, quota and conveniencesampling are often used; of these,quota sampling is preferred because itis less prone to bias.Cluster SamplingCluster sampling is the most widely usedtype of probability sampling and is usefulor most types of ARH program evaluations.It involves two stages:First, identify groups that you want tocollect data from, such as schools,acilities or youth clubs.
Thesegroups are clusters.Next, make a listof all the clusters; this is your samplingame.A sample of clusters is thenselected from this list.Now develop a list of sample elementswithin your selected sample clusters,acility clientsor youth club members.Then select a.The result is the sample of individualsFor example, suppose your organizationhas a peer education program in 40 schools.Each school would be considered a cluster.First you would select a sample of schoolsfrom among the 40 involved in theam.
Then you would select a randomsample of students within each schoolA Guide to Monitoring and Evaluating Adolescent Reproductive Health ProgramsAdvantages and Disadvantages of Probability and Non-Probability Sampling MethodsType of Sampling Method
sampling error, from which you can
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