# sampling plans

 The flashcards below were created by user jam110007 on FreezingBlue Flashcards. population The aggregate of cases in which a researcher is interested sampling Selection of a portion of the population (a sample) to represent the entire population Eligibility criteria The characteristics that define the population- inclusion criteria - exclusion criteria strata Subpopulations of a population (e.g., male/female) Target population The entire population of interest Accessible population The portion of the target population that isaccessible to the researcher, from which a sample is drawn Representative sample A sample whose key characteristics closely approximate those of the population—a sampling goal in quantitative research Sampling Goal for Quantitative Research is to obtain a sample that represents the population representative sample is more easily achieved with Probability samplingHomogeneous populationsLarger samples Sampling Problems for Quantitative Research sampling errorsampling bias sampling bias The systematic over- or under-representation of segments of the population on key variableswhen the sample is not representative Sampling error Differences between sample values and population values sampling designs probability samplingnon-probability sampling Probability sampling Involves random selection of elements: each element has an equal, independent chance of being selected Nonprobability sampling Does not involve selection of elements at random Not all people have an equal chance of being selected Non-Probability Sampling include ? Convenience sampling Snowball (network) sampling Quota sampling Purposive sampling Convenience Sampling a form of non probability sampling  use of the most convenient available people most widely used approach by quantitative researchers most vulnerable to sampling bias - may not represent the overall population snowball sampling a form of non probability sampling  referrals from other people already in sample used to identify people with distinctive characteristics  used by both quantitative and qualitative researchers Quota Sampling a form of non probability sampling  Convenience sampling within specified strata of the population Goal is to Enhance the representativeness of sample Infrequently used, despite being a fairly easy method of enhancing representativeness Consecutive Sampling a form of non probability sampling  Involves taking all of the people from an accessible population who meet the eligibility criteria over a specific time interval, or for a specified sample size A strong nonprobability approach for “rolling enrollment” type accessible populations Risk of bias low unless there are seasonal or temporal fluctuations Purposive Sampling a form of non probability sampling  Sample members are hand-picked by researcher to achieve certain goals Used more often by qualitative than quantitative researchers Can be used in quantitative studies to select experts or to achieve other goals Types of Probability Sampling Simple random sampling Stratified random sampling Cluster (multistage) sampling Systematic sampling Simple Random Sampling form of probability sampling Uses a sampling frame – a list of all population elements Involves random selection of elements from the sampling frame Not to be confused with random assignment to groups in experiments Cumbersome; not used in large, national surveys Stratified Random Sampling type of probability sampling  Population is first divided into strata, then randomselection is done from the stratified sampling frames Enhances representativeness- Can sample proportionately or disproportionately from the strata Cluster (Multistage) Sampling type of probability sampling  Successive random sampling of units from larger to smaller units (e.g., states, then zip codes, then households) Widely used in national surveys Larger sampling error than in simple random sampling,but more efficient Sample Size The number of study participants in the final sample Sample size adequacy is a key determinant of sample quality in quantitative research. Sample size needs can and should be estimatedthrough power analysis. Sampling for Qualitative Research Selection of sample members guided by desire for information-rich sources “Representativeness” not a key issue Random selection not considered productive Sampling Methods for Qualitative Reserach Sampling Methods for Qualitative Reserach Convenience (volunteer) sampling Snowball sampling Purposive sampling Theoretical sampling Theoretical Sampling Preferred sampling method in grounded theory research Involves selecting sample members who best facilitate and contribute to development of the emerging theory Sample size for Qualitative Research No explicit, formal criteria Sample size determined by informational needs Decisions to stop sampling guided by data saturation Data quality can affect sample size. Sampling for Ethnography Mingling with many members of the culture—a “big net” approach Informal conversations with 25 to 50 informants Multiple interviews with smaller number of key informants Sampling for Phenomenology Relies on very small samples (often 10 or fewer) Participants must have experienced phenomenon of interest Sampling for Grounded Theory Typically involves samples of 20 to 40 people Selection of participants who can best contribute to emerging theory (usually theoretical sampling) Authorjam110007 ID250838 Card Setsampling plans Description3215 final Updated2013-12-05T01:56:59Z Show Answers