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Sampling and Theory Flashcards

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6327592313What is sampling?A sample is a subset taken from the target population (population of interest)0
6327687741populationThe population shares common characteristics that you, the researcher, define before your study begins.1
6327695511target populationTarget population is the group from which you can select a sample (from the population you have defined)2
6327786747Sampling PlanHow you put it all together and follow through with design - Qualitative, Quantitative?3
6327704845Quantitative Sampling (usually probability)• Sample determines external validity (can you generalize your findings from the sample to the population (hopefully) • And to some extent, internal validity (can you rule out all other alternative explanations for the results4
6327719955Steps in Sampling• Define the population • Develop a plan - how you will select a sample • Determine the size • Select the sample • Compare if the sample truly represents the characteristics of the population.5
6327888553power analysisused to calculate the minimum sample size required so that one can be reasonably likely to detect an effect of a given size6
6327730378Probability Sampling (usually for quantitative)• Everyone has an equal chance of being selected • Random - one step do it all • Systematic - select from pre-set intervals • Stratified -fixed % randomly drawn from pre-divided subgroups • Cluster - randomly, sequentially drawn from already existing larger subgroups7
6327742451Examples of Clustering• Random - assign each individual a number and choose the numbers from a pile of numbers. • Systematic - assign each individual a number and choose odd numbers • Stratified - Determine % of patients that are male or female and choose those % in your sample8
6327754381Non-Probability Sampling (usually for qualitative)• Do not know the parameters of the population therefore use non-random methods of selection • Convenience-what is available • Purposive-particular characteristics that fit your criteria but non-random • Snowball- word of mouth networking • Quota- set number of subgroups according to the population characteristics but non-randomly9
6327761960Relation of Sampling to Validity• External validity means that you can accurately generalize the findings from your sample the population. • If the selection of the participants is biased then the results of the study cannot be generalized to a larger population. • Selective effects (error in sampling and selection) is a threat to external validity.10
6327768835Qualitative Sampling (usually non-probability)• Is purposive - choose those who can offer the most relevant information about your topic • Typically, establish criteria or what you want to include then find participants who fit the bill11
6327776950Boundary SettingCan choose a sample and further bound the study by choosing: setting, stories, groups, images, experiences, concepts, objects12
6327818978Sampling - Qualitative Characteristics• Typical- the majority • Extreme or deviant- most extreme to compare to the majority • Comprehensive/Maximum Variation-all the participants or cases that match the criteria are included • Confirming or Disconfirming • Reputational- recommended by experts • Comparable- select cases with the same characteristics that match the criteria over a period of time. • Convenience- can be included most quickly or conveniently13
6327820886Sampling size, what is reasonable?Quantitative - large size, minimum 30 per variable, but do POWER analysis to confirm sample is large enough Qualitative - small size, 3-5, or single subject14
6328056026Saturationqualitative - you've interviewed so many people that you start to get no new info15
6327842676Why is theory important in quantitative research?Guides your decisions: problem statement, which variables to measure, setting boundaries, data collection, analysis, But HELPS TO SEE THE BIG PICTURE16
6327846538Why is theory important in qualitative research?develop a theory, interpret data17
6327874987what is theory?• Inter-related concepts (observation), constructs (surmised, categories), relationships, propositions (statements that govern the relationships, suggestions) that can explain or predict human experience - and make it orderly. • Deductive- verify or refute • Inductive- explain, develop18

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