| Definition | Define the analytical purpose in plain language. | Classify the outcome and explanatory variables. | Identify groups, pairing, sampling, and dependence. | Name the population quantity or relationship. | Select a candidate procedure from the purpose and structure. | Examine conditions that make the method credible. | Read estimates, intervals, model fit, and p-values together. | Translate the result into a bounded conclusion. |
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| Primary decision question | Are you describing, comparing, relating, predicting, or estimating? | Which variable is numeric or categorical, and what role does each play? | Are observations independent, matched, repeated, or clustered? | Is the target a mean, difference, proportion, association, or slope? | Which method answers this target with these variables and observations? | What must be true about design, form, distribution, variance, or observations? | What result answers the question, and how uncertain is it? | What does the evidence support, not support, and leave uncertain? |
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| Purpose | Prevents method-first reasoning. | Narrows the valid method family. | Protects the uncertainty calculation. | Aligns hypotheses and output. | Creates an explainable selection. | Tests whether the candidate is defensible. | Balances evidence strength and magnitude. | Produces responsible communication. |
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| Time horizon | Before opening software | Question design | Data provenance review | Before computation | Analysis planning | Before final output | Output review | Final interpretation |
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| Typical information | A one-sentence research question | Variable definitions, units, and coding | How observations were obtained | A parameter stated in context | A method-selection rationale | Design facts, plots, and diagnostics | Estimate, units, interval, test or model diagnostics | Context, limitations, and next question |
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| Common confusion | Naming a procedure instead of a question | Treating numeric labels as quantities | Assuming rows are automatically independent | Writing hypotheses about sample results | Choosing by keyword alone | Treating a software result as self-validating | Reporting only significant or not significant | Turning uncertainty into certainty |
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| What does not belong | No method selected yet | No interpretation without units | No population claim beyond the design | No vague claim such as there is a difference | No guarantee that assumptions hold | No cosmetic assumption checklist | No causal claim from association alone | we explain; you submit your own work |
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