Researchers follow two groups for the same length of time. The groups are similar in age and in other factors that may affect cancer risk.
| Group | Human papillomavirus (HPV) status | People followed | People developing cervical cancer |
|---|---|---|---|
| V | persistent HPV infection | 300 | 24 |
| W | no persistent HPV infection | 600 | 12 |
A researcher writes:
“The risk in group V is twice the risk in group W because 24 is twice 12. Persistent HPV increases cancer risk by destroying white blood cells.”
Which comment correctly identifies the error or errors in the researcher's interpretation?
Both points need correcting: the risk in V is fourfold the risk in W, and persistent HPV can disrupt the control of cell division.
Only the mechanism needs correcting: the risk in V is twice the risk in W, but persistent HPV can disrupt the control of cell division.
Both points need correcting: the risk in V is fourfold the risk in W, and persistent HPV destroys white blood cells that coordinate immune responses.
The groups cannot be compared because their sizes differ, although persistent HPV can disrupt the control of cell division.
112 exam-style questions on Edexcel GCSE Biology 5.1 Health and communicable disease, covering 5.1.1 Communicable and non-communicable diseases, 5.1.2 Disease susceptibility interactions, 5.1.3 Pathogens as disease-causing organisms, 5.1.4 Common infections, 5.1.5 Spread and prevention of pathogens, 5.1.6 Lifecycle of a virus, and 5.1.7 Spread and prevention of STIs. Each one has a worked solution and a mark scheme showing where the marks go.