A clinic introduced invitations for regular chlamydia testing.
The table shows the results for equal periods before and after the invitations were introduced.
| Period | Number of people tested | Number who tested positive |
|---|---|---|
| before invitations | 800 | 64 |
| after invitations | 1600 | 96 |
Which statement is supported by the data?
The proportion testing positive was lower after invitations, but these data do not establish that the invitations caused the decrease.
The proportion testing positive was unchanged because both the number tested and the number testing positive increased.
The proportions cannot be compared because a different number of people was tested in the two periods.
The proportion testing positive was higher after invitations, although other factors might have caused the increase.
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.