Past exam of the mathematics course of the University of Cambridge 2021 ii Paper 1 13J a i Solution Created 2026-09-24 Updated 2026-09-25
Let be the count for treatment(Control, LD, or SD) and outcome(Better or Worse), and write . Both fits take the six cell counts to be independent Poisson variables.
The additive log-linear model fitted by
fit1 iswith reference constraints and . Thus treatment changes the overall group count but not the relative frequencies of the two outcomes.