مقایسهٔ روش‌ها

	انواع طرح تحقیق	روش‌های نمونه‌گیری در پژوهش
حوزه	روش‌شناسی پژوهش	روش‌شناسی پژوهش
خانواده	Process / pipeline	Process / pipeline
سال پیدایش	1963	1950
پدیدآور	Donald T. Campbell and Julian Stanley (1963); William Shadish, Thomas Cook, & Donald Campbell (2002)	William G. Cochran and Leslie Kish (1950s–1970s)
نوع	Framework	Framework
منبع بنیادین	Campbell, D. T., & Stanley, J. C. (1963). Experimental and Quasi-Experimental Designs for Research. Rand McNally.	Cochran, W. G. (1977). Sampling Techniques (3rd ed.). John Wiley & Sons.
نام‌های دیگر	research designs, experimental and observational designs	sampling strategy, sampling design, probability and non-probability sampling
مرتبط	3	3
خلاصه	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 qualitative (exploratory, interpretive). Donald T. Campbell and Julian Stanley's 1963 seminal work established systematic terminology for internal validity threats in each design type. Modern classifications (Campbell et al., 2002; Creswell & Plano Clark, 2011) also include mixed-methods designs combining quantitative and qualitative elements.	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, systematic sampling—enable statistical inference to the population and allow calculation of confidence intervals and margins of error. Non-probability methods—convenience, purposive, snowball, quota sampling—are practical for exploratory or qualitative research but do not support formal statistical generalization. Cochran's Sampling Techniques (1977) and Kish's Survey Sampling (1965) are foundational references; modern applications span surveys, experiments, qualitative studies, and clinical trials.