Sampling error is only one limit. Coverage error occurs when some members of the target population cannot enter the frame. Nonresponse matters when participants differ from those who decline. Mode, wording, order, and social desirability can affect answers. Weighting can adjust known imbalances but does not eliminate every error or create information from a very small subgroup. A reported margin of error generally describes sampling variation under the design, not all of these nonsampling problems.

Turnout and party support must also remain separate. A party can gain statewide vote share because voters changed preferences, because its supporters participated at higher rates, or because the electorate's composition changed. If younger voters become a larger share of participants and already favor the party, the overall result can move even when support within every age group stays constant. Compare within-group rates and each group's weight before declaring a broad preference shift.

Every important word in a claim makes an evidentiary demand. "Most" requires a value above half for the stated population. "Increased" requires a comparable earlier measure. "More likely" requires rates with consistent denominators. "Caused" requires a design that addresses alternatives. "Will" requires a defensible forecast. A table showing two cross-sections can document change without explaining it.

Different sources answer different parts of a question. Certified returns are strong evidence about counted votes but weak evidence about motives. Surveys measure attitudes and reported behavior but contain sampling and response error. Validated administrative records can confirm participation while preserving ballot secrecy. Experiments may estimate an effect in a narrower setting. Combining sources is valuable when each one supports a distinct link rather than when several weak sources merely repeat the same assumption.

Use a final claim check: name the population, unit, outcome, denominator, time, comparison, uncertainty, and causal verb. If the evidence does not support one element, narrow the sentence. A precise conclusion is not a lesser answer. It is the strongest answer whose every word can be defended.

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