Table 1.

Coding framework for classifying evidence

	Evidential criteria	Use in previous studies	Data coding framework	Coding categories
Relevance	Subject matter	What is the topic, argument, position or conclusion of the evidence?40–42	What issue does the research address?	▸ Standardised packaging of tobacco ▸ Tobacco packaging, eg, graphic health warnings ▸ Tobacco, not packaging ▸ Unrelated to tobacco
Quality	Independence	Who funded the evidence? Are authors affiliated to the tobacco industry?39–42	Who funded the research? Has the author of the research any connection with the tobacco industry?	▸ Tobacco industry-funded (statement included that the research was funded by the tobacco industry) ▸ Tobacco industry-linked (no statement that the research was funded by the tobacco industry, but evidence of other connection: eg, author or funder have prior links to the tobacco industry) ▸ Independent of the tobacco industry (statement included that the research was funded by a source independent of the tobacco industry) ▸ No apparent tobacco industry connection (no information provided about funding source and no evidence of prior connection with the tobacco industry)
	Peer-review status	Has the evidence been peer-reviewed? What is the impact factor of the journal and date of publication?39–42	Was the research published in peer-reviewed journal? If not, where was the research published?	▸ Peer-reviewed journal ▸ Academic press volume ▸ Conference paper ▸ Government-commissioned research ▸ University research report ▸ Government internal research ▸ Charity research report ▸ Private company research report ▸ Unpublished