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Data saturation is a foundational principle in qualitative research describing the point at which data collection yields no new themes, codes, or insights—additional data becomes redundant. Introduced by Glaser and Strauss (1967) in their work on grounded theory, saturation guides decisions about sample size and when t
Document analysis is a systematic qualitative research method for examining written, visual, or audiovisual sources—such as policy documents, historical records, organizational records, media reports, emails, social media posts, photographs, or videos—to extract meaning, identify patterns, and understand social phenome
Qualitative Content Analysis (QCA) is a systematic, inductive method for analyzing textual or visual data by identifying and categorizing meaning units into content categories. Developed and formalized by Klaus Krippendorff (1980), QCA can be purely qualitative (inductive, exploratory) or combined with quantitative cou
Thematic Analysis (TA) is a qualitative research methodology for identifying, analyzing, and reporting patterns (themes) in qualitative data. Developed systematically by Virginia Braun and Victoria Clarke (2006), TA is flexible and accessible, applicable across diverse theoretical frameworks and data types, making it o
Action research is a collaborative research methodology in which researchers work with practitioners and community members to investigate a problem, implement change, and evaluate outcomes, cycling through reflection, action, and learning. Developed by Kurt Lewin (1946), action research bridges research and practice, a
Case study research is an intensive, contextual investigation of a single case (or small number of cases) to explore a phenomenon in depth. Developed systematically by Robert K. Yin (1984) and Robert E. Stake (1995), case study research employs multiple data sources (interviews, observation, documents, artifacts) to pr
The Critical Appraisal Skills Programme (CASP) RCT Checklist is a practical, widely adopted tool developed by the UK-based Critical Appraisal Skills Programme (founded 1993) for assessing the methodological quality and relevance of published randomized controlled trials. Unlike numeric scoring scales, it uses 11 struct
The CONSORT (Consolidated Standards of Reporting Trials) Statement is a 25-item evidence-based checklist and flow diagram developed to standardize reporting of parallel-group randomized controlled trials. First published in 1996 and updated in 2010 (CONSORT 2010), it is endorsed by over 600 journals including The Lance
COSMIN (COnsensus-based Standards for the selection of health Measurement INstruments) is a systematic framework and 10-item checklist developed by Mokkink et al. (2010) to evaluate the methodological quality of studies that assess the measurement properties of patient-reported outcome measures (PROMs), questionnaires,
Data collection methods are the specific techniques and instruments used to gather information from research participants or sources. Common quantitative methods include surveys (questionnaires, interviews), physiological measurements (blood pressure, lab assays), behavioral observations, and administrative/secondary d
Discourse analysis is a qualitative research methodology that examines how language, communication, and power shape meaning, identity, and social reality. Developed across linguistics, sociology, and psychology (particularly by Norman Fairclough and Jonathan Potter), discourse analysis goes beyond content to analyze la
Ethnographic research is an immersive qualitative methodology in which researchers spend prolonged time in a community, organization, or social setting, combining participant observation, interviews, and document analysis to develop a rich, contextual understanding of a group's beliefs, practices, and social structures
Focus group discussions are a qualitative research method in which a trained moderator guides a small group (typically 6–12 participants) through structured or semi-structured discussion of a specific topic or product. Developed by Merton and Lazarsfeld in the 1950s for market research, focus groups are now widely used
Grounded Theory (GT) is a systematic qualitative research methodology in which theory emerges directly from data through iterative analysis, rather than being imposed before data collection. Developed by Barney Glaser and Anselm Strauss in 1967, GT prioritizes generating explanatory frameworks grounded in evidence.
A hypothesis is a testable prediction or proposed explanation for a phenomenon, expressed as a relationship between variables. Hypothesis development is the process of formulating null hypotheses (H₀, asserting no effect or relationship) and alternative hypotheses (H₁, asserting an effect or relationship) before data c
In-depth interviews are a qualitative research method in which a trained interviewer conducts one-on-one conversations with individual participants using open-ended questions to explore their experiences, perspectives, and understandings of a phenomenon. Developed in the 1950s by Rogers and Hyman, the method varies alo
Interpretative Phenomenological Analysis (IPA) is a qualitative research methodology that explores how people make sense of significant personal experiences. Developed by Jonathan Smith (1999) and grounded in phenomenology and hermeneutics, IPA examines individual experience in detail before identifying shared patterns
JBI (Joanna Briggs Institute) Critical Appraisal Tools are a comprehensive suite of design-specific quality assessment instruments developed by the Joanna Briggs Institute (University of Adelaide, Australia) since 1998. Unlike single-tool approaches, JBI offers over 15 separate checklists tailored to RCTs, cohort studi
Member checking is a quality assurance procedure in qualitative research in which the researcher shares preliminary findings, interpretations, or analytical themes with research participants and asks whether the findings accurately reflect their perspectives and experiences. Developed by Lincoln and Guba (1985) as a tr
MMAT (Mixed Methods Appraisal Tool) is a practical, design-agnostic quality assessment tool developed by Pluye et al. (2014, updated 2018) to evaluate the methodological quality of quantitative (RCTs, non-randomized studies), qualitative, and mixed-methods studies. Unlike tools designed for single paradigms (e.g., Coch
Narrative inquiry is a qualitative research methodology that treats stories and life narratives as primary data, analyzing how individuals construct meaning and identity through storytelling. Developed by D. Jean Clandinin and F. Michael Connelly (2000), narrative inquiry examines the narratives people tell about their
The Newcastle-Ottawa Scale (NOS) is a widely used tool for assessing the methodological quality of observational studies (case-control and cohort designs) included in systematic reviews and meta-analyses. Developed by Wells et al. at Ottawa Hospital in 2000, it provides explicit criteria and a star-based scoring system
NVivo and ATLAS.ti are Computer-Assisted Qualitative Data Analysis Software (CAQDAS) programs that facilitate coding, organizing, and analyzing qualitative data—including text (transcripts, documents), images, video, and audio. NVivo, developed by QSR International, is widely used in academic research and supports data
Participant observation is a qualitative research method in which the researcher embeds themselves within a community, organization, or social setting for an extended period, engaging in the activities and relationships of the group while systematically observing and documenting behavior, interactions, and cultural mea
Phenomenological research is a qualitative methodology focused on understanding the lived experience of a phenomenon as it is experienced by individuals. Rooted in the philosophical traditions of Edmund Husserl (descriptive phenomenology) and Martin Heidegger (interpretive phenomenology), this approach seeks to uncover
Qualitative research is a systematic inquiry into human experiences, meanings, behaviors, and contexts using non-numerical data (words, text, images, observations). Unlike quantitative research, which seeks to measure variables and test hypotheses numerically, qualitative research prioritizes depth, contextual richness
Reflexivity is the practice of examining how the researcher's identity, assumptions, relationships, and values influence the research process and findings. Rather than treating objectivity as achievable detachment, reflexivity acknowledges that the researcher is embedded within the research and cannot be fully separate
Research design is the overall structure and strategy of a study, encompassing decisions about how to collect, organize, and analyze data to answer research questions. Major design types include experimental (randomized controlled trials), quasi-experimental (non-random assignment), observational (no manipulation), and
Research question formulation is the process of defining clear, focused, and answerable questions that guide a research study. A well-formulated research question specifies what a researcher seeks to investigate, distinguishing between independent and dependent variables (or phenomena), and sets the scope for literatur
Sampling is the process of selecting a subset of individuals, observations, or units (the sample) from a larger population to study. Sampling methods are broadly classified into probability (random) and non-probability (non-random) approaches. Probability methods—random sampling, stratified sampling, cluster sampling,
STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) is a 22-item evidence-based checklist published in 2007 by Von Elm et al. to improve the quality of reporting of cohort, case-control, and cross-sectional observational studies. Like CONSORT for RCTs, STROBE is endorsed by over 300 journals a
Trustworthiness is a framework for evaluating the quality and rigor of qualitative research, developed by Lincoln and Guba (1985) as an alternative to quantitative criteria (internal validity, external validity, reliability, objectivity). The framework comprises five criteria: credibility (findings are accurate and gro
Validity and reliability are two foundational concepts in research quality. Reliability refers to the consistency and reproducibility of measurements: do repeated applications of an instrument yield the same results? Validity refers to the truthfulness of inferences: does an instrument measure what it claims to measure