title: Divergent biases in ecologic and individual level studies.
authors.forename: B L
authors.initials: BL
authors.lastname: Cohen
mesh_terms: D015982:Bias; D004463:Ecology; D006801:Humans; D008175:Lung Neoplasms / Q000209:etiology*; D012044:Regression Analysis; D012907:Smoking / Q000009:adverse effects*