Interaction

Question 1

Interaction (effect modifier)

Answer 1

Comparing one variable to another. Notion of heterogeneity ie the interaction between sex and treatment implies the effect of treatment is different between the sexes

Question 2

Tests used to detect and quantify effect

Answer 2

t-test, chi-squared, ANCOVA

Question 3

P-value

Answer 3

Composite which depends on the size of the effect but also how precisely the the effect has been estimated (SE)

Question 4

Selection of subgroups

Answer 4

Should be prespecified during trial design . Treat unanticipated subgroup findings with caution