| Definition | Summarize observed data without generalizing beyond the evidence. | Represent uncertainty with a suitable event or random-variable model. | Use sample evidence to give a plausible range for a population parameter. | Evaluate how compatible observed evidence is with a specified null model. | Quantify association and, when appropriate, use a fitted relationship for prediction. |
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| Primary decision question | What pattern, center, spread, category share, or unusual value is present? | Is the target one event, a sequence, a count of successes, or a standardized value? | Is the target a mean, proportion, difference, or another supported parameter? | What claim, parameter, direction, grouping, and pairing define the hypotheses? | Are two quantitative variables being associated, explained, or predicted? |
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| Purpose | Build an honest picture before inference. | Calculate likelihoods under explicit conditions. | Report magnitude together with uncertainty. | Make a calibrated evidence decision. | Summarize direction, strength, fitted change, and residual variation. |
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| Time horizon | Before estimating, testing, or predicting. | After defining outcomes and dependence. | After checking design and interval conditions. | After hypotheses and assumptions are fixed. | After plotting and checking the observed range. |
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| Typical information | Variable type, distribution shape, units, and sample summaries. | Sample space, event relationship, trial count, probability, or distribution parameters. | Point estimate, standard error, critical value, and confidence level. | Test statistic, null reference model, p-value or critical rule, and significance level. | Scatterplot, correlation, regression coefficients, coefficient of determination, and residuals. |
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| Common confusion | Choosing the mean automatically for a skewed distribution. | Multiplying probabilities when events are dependent without using a conditional probability. | Interpreting confidence as the fraction of observations inside the interval. | Treating failure to reject as proof of no effect. | Using a strong fit as proof of causation. |
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| What does not belong | Do not call a sample statistic a population fact. | Do not impose a binomial model when trials or success probabilities do not fit. | Do not ignore sampling bias because an interval is narrow. | Do not change a one-sided direction after seeing the data. | Do not extrapolate far beyond the observed explanatory values. |
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