Which was the main reason why the UNAIDS estimates of HIV ...

[jace]

Which was the main reason why the UNAIDS estimates of HIV prevalence in India before 2007 were too high?
 
  a) No data on HIV were collected, and the estimates were based on guesses by health professionals.
  b) There was political opposition of the collection of data about HIV.
  c) The results of surveys were falsified.
  d) Estimates were based on surveys of groups with a high HIV prevalence, such as injection drug users and commercial sex workers.

Question 2

An advantage of a longitudinal survey over a series of cross-sectional surveys is which of the following?
 
  a) It is easier to trace the same people over time in a longitudinal survey than to do a series of cross-sectional surveys.
  b) A longitudinal survey remains representative of the population as a whole, while a series of cross-sectional surveys quickly becomes unrepresentative of the population.
  c) A longitudinal survey is less affected by refusal of respondents to participate than is a series of cross-sectional surveys
  d) A longitudinal survey can trace changes in individual persons or households over time.

[xthemafja]

Answer to Question 1

d

Answer to Question 2

d