What is research design?

Research design = the research's blueprint — the plan that specifies, before the work begins: what is studied (the questions/hypotheses), where and on what (the population, the sample), with what instruments (the tools), by what procedure (the sequence and the controls), and how the data will be analysed — so that the evidence collected actually answers the question asked. The classic image: the architect's plan before the building — the design's flaws become the study's structural flaws, discovered too late. Its nature: (i) forward-looking — committed before the data (the proposal's core, U3.4); (ii) integrative — it binds the problem, the approach (U2), the tools (U5) and the analysis (U6) into one coherent plan; (iii) a series of decisions — the what/ where/how/when questions answered deliberately, not drifted into; (iv) a control device — the design's whole point is to exclude the rival explanations (the confounders) so the conclusion follows from the evidence.