Sources and level of evidence

A source is useful only for the claim it can support. A definition, a causal estimate, a benchmark and an implementation guide require different evidence. Marketing Mix in Action therefore states the source’s role, scope and limits rather than treating prestige as a substitute for applicability.

Prefer primary and inspectable material

Scientific papers, standards, methodological documentation, original datasets and institutional publications are preferred for technical or quantitative claims. An important statement should point to material that can be consulted directly, with a date, scope and locator where the conclusion depends on it.

Check comparability before transfer

Compare population, period, unit, method, exclusions and outcome definition before importing a value into a decision. A precise number from another context is not automatically relevant. When these conditions are missing, the number is context only—not a planning parameter.

Publish disagreement and uncertainty

When credible methods or results diverge, the divergence should remain visible. Identify which decision remains robust and what new information could discriminate between options. A bibliography at the bottom of a page does not replace adjacent support for a calculation or causal conclusion.