The table is organized to allow an evaluation of effect measure modification. Which of the following statements identifies and justifies the method of assessment for effect modification as either joint effects or heterogeneity of effects?

Maternal HIV status Mother has Incidence at child's birth comorbid illness? Rate 95% CI Ratio (IRR) Neg No 1.0 REFERENCE Positive No 2.0 0.75 - 5.32 Neg Yes 2.5 1.53 - 4.08 Positive Yes 5.0 3.06 - 8.16