Module 9 - Sampling EDRE 5774: Introduction to Mixed Methods

MM Sampling “MM sampling involves combining well- established qualitative (QUAL) and quantitative (QUAN) in creative ways to answer the research questions posed by the MM research designs.” (T & T, p. 169) “…the researcher’s ability to creatively combine these sampling techniques is one of the defining characteristics of MM research.” (T & T, p. 180) EDRE 5744: Introduction to MM Research2

Two Major Approaches to Sampling Probability Sampling – Primarily associated with QUANT – What allows for claim of generalizability – Produces understanding of breadth or variance in the phenomenon under study Purposive Sampling – Primarily associated with QUAL – Aims for transferability to similar contexts – Produces in-depth understanding of the phenomenon under study EDRE 5744: Introduction to MM Research3

Similarities between Probability and Purposeful Sampling Both are designed to answer the research questions. Both are concerned with issues of external validity. – QUANT – generalizable – QUAL - transferability EDRE 5744: Introduction to MM Research4

Differences between the two Sampling Approaches ProbabilityPurposeful Sample size – large enough to establish representativeness Typically small (30 or fewer) Focuses on breadth of information from a wide-range of cases. Focuses on depth of information from a small number of cases, but the cases could cover a wide range. Timing of sample selection – during design phase, before the study begins Before the study begins, but also during the study Method of Selection method - formal or procedural (e.g random table generator) Features judgment more prominently EDRE 5744: Introduction to MM Research5

Sampling Viewed from the Design Level Single Phase/Strand StudiesMultiple Phase/Strand Studies Include both Purposeful and Probablity Sampling Stratified purposive samplingParallel MM sampling Purposive random samplingSequential MM sampling Multi-level MM sampling EDRE 5744: Introduction to MM Research6

MM Sampling in Single Phase Studies Examples in Single Phase/Strand Studies Combines probability and purposeful sampling Stratified purposive samplingResearcher identifies sub-groups; then selects small number of cases in a purposeful manner from each sub-group Purposeful random samplingRandom sample of a small number of units from a much larger population EDRE 5744: Introduction to MM Research7

Creamer & Ghoston (2012) Sampling Plan One phase of data collection One type of sampling - Stratified Random Sampling – a QUANT sampling strategy No purposeful (QUAL) sampling Sampling frame allowed for claim of generalizability. EDRE 5744: Introduction to MM Research8

Sampling In Multi-Phased Studies Multiple Phase/Strand Studies Include both purposeful and probability sampling Generally a different sampling strategy per phases Parallel, sequential, and multi-level sampling EDRE 5744: Introduction to MM Research9

Elegant Sequential Sampling Plan by Ivankova and Stick (2007) Phase 1 QUANT – cross-sectional web-based survey of 278 current and former students Phase 2 QUAL – – 4 purposefully selected “typical case” respondents based on mean score on scale items – Then used maximal variation to get a mix by gender, age, residency, family status EDRE 5744: Introduction to MM Research10

Multi-Level Sampling Plan in a Teacher Effectiveness Study LevelSampling Plan DistrictsCould be stratified by size or urban/rural SchoolsCould be stratified by effectiveness measure TeachersLikely to be purposeful sampling StudentsLikely to be random sampling EDRE 5744: Introduction to MM Research11

Concluding Points about Sampling The sampling plan determines whether you have the potential to make claims of generalizability to your study. In most MM studies, it combines purposeful and probability strategies. Creative combinations of sampling strategies can give your study both breadth and depth. EDRE 5744: Introduction to MM Research12