title: Interaction revisited: the difference between two estimates.
authors.affiliation: Cancer Research UK Medical Statistics Group, Centre for Statistics in Medicine, Institute for Health Sciences, Oxford OX3 7LF. doug.altman@cancer.org.uk
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Altman
authors.forename: J Martin
authors.initials: JM
authors.lastname: Bland
mesh_terms: D000704:Analysis of Variance; D016001:Confidence Intervals; D013223:Statistics as Topic