We need to identify a reason which can cause the increase in cancer risk in left handed women as compared to right-handed women.
A – Wrong
This is actually a correct technique to use. The value for cancer risk in left handed women will be relative to 1.
B – Wrong
This is not related to left-handedness
C – Wrong
We need to identify why cancer risk in left handed women is higher than risk in right-handed women. This does not give us a cause of the increased risk.
D – Correct
D gives us a cause for the correlation observed in the study.
E – Wrong
The relative risk takes into account the number of people present in the group so this does not cause any bias.